NBSIR 74-598 /f)

Electrodeposition of Chromium with

Periodic Reverse and Pulsed Current

John P. Young

Corrosion and Electrodeposition Section

Metallurgy Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

October, 1974

Final Report

Prepared for Research Directorate

Weapons Laboratory • RIA

Rock Island Arsenal

Rock Island, Illinois 61201

NBSIR 74-598

ELECTRODEPOSITION OF CHROMIUM WITH

PERIODIC REVERSE AND PULSED CURRENT

John P. Young

Corrosion and Electrodeposition Section

Metallurgy Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

October, 1974

Final Report

Prepared for Research Directorate

Weapons Laboratory - RIA Rock Island Arsenal

Rock Island, Illinois 61201

U. S. DEPARTMEIMT OF COMMERCE, Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

Table of Contents

Abstract

Objective

Page

Introduction 1

Equipment 4

Procedure 5

Experimental Results of PR Tests 7

Cycle-time length tests ' 7

Bath concentrations 9

Effect of coating backs of specimens 11

Current density tests 12

Reverse current levels 14

Additives in the chromium bath 16

Oxalic acid 16

Boric acid 18

Sodium hydroxide 19

Sodium chloride 20

Sodium carbonate 21

Bath temperature and deposit appearance 22

Cross-sections of PR deposits 23

Combinations of favorable conditions 24

Screw threads plated with PR chromium 25

Summary of PR Plating Tests 27

Equipment for Pulse Current Tests 28

Results of Pulsed Current Tests 29

Exploratory pulse-time and pulse-level tests 29
-2-

Page

Pulse-time variables at 65 and 55°C 29

Pulse base level test • 30

Hardness tests of deposits 31

Pulse ratio tests at 33 and 50% pulse base level 31

Duplication of low ratio deposits 32

Pulsed current and the dilute CrO^ bath 32

Pulsed current and the concentrated CrO^ bath 33

Current control of pulse level 33

Summary of pulse plating tests 34

Concl usion , 35

Bibliography

Appendix - Tabulation of Test Data
ABSTRACT

This report covers an investigation of the effects of periodic reverse

current and pulsed direct current on properties and metal distribution of chromi

-^electrodeposits . The plating current was reversed for short periods of various

lengths during deposition of chromium at various current densities and in baths

at several concentrations of chromium trioxide or CrO^. Several chemicals

were added to the standard bath in an effort to further improve deposit

distribution during periodic reverse (PR) plating. Several of the chemicals tried as well as the lower bath concentrations were effective in

improving distribution in addition to the improvement obtained with PR.

Thickness ratios of less than one were obtained on some panels and screw

threads were plated with a ratio as low as 1.3 using PR. Small but

definite improvements in the distribution of chromium deposits were obtained using pulsed dc current with the most uniform thickness obtained

in the dilute bath. Also, nearly all deposits from the dilute bath were

bright over a range of pulse times.

OBJECTIVE

Explore the use of periodic reverse current for the improvement

of the distribution of chromium deposits in the standard chromium bath

with or without the addition of various chemicals to enhance the effect

of PR. Determine the practical operating conditions of the PR plating

process and the properties of the chromium deposits obtained. Investigate the use of pulsed direct current (PC) for the improvement of distribution and properties of chromium deposits.

ELECTRODEPOSITION OF CHROMIUM WITH PERIODIC

REVERSE AND PULSED CURRENT

Introduction .

Some work has been done using periodic reverse current (PR) for plating

chromium with resulting claims for improved adhesion, deposit distribution

and greater density of the deposit, etc. The work is detailed in items

listed in the bibliography at the end of this report. PR is effective

in producing deposits of uniform thickness with little edge build-up and

with smooth, bright surfaces from copper, silver, and gold cyanide baths.

It has been used with only a few other plating solutions. The deposition

of chromium results in excessive build-up of the deposit on edges and corners

and on areas nearest the anode. This work investigated various combinations

of forward and reverse current cycles and pulsed current (PC) times and

levels to improve chromium deposit thickness distribution.

There are several differences in plating from a chromic acid bath and

from the cyanide baths that are used successfully with PR and PC. The

cyanide baths tend to form a resistant cathode layer which becomes more

resistant the higher the current density. Chromium is more efficiently

deposited at higher current densities. Due to the generally low efficiency

(12-15%) of chromium deposition, there is a copious release of hydrogen

which causes considerable agitation at the cathode surface. This condition

does not occur in most cyanide baths at normal plating conditions. Also the

cyanide baths are alkaline and mildly oxidizing while the chromium bath is

strongly acid and strongly oxidizing. The great dissimilarity of the two

gives no hint for the successful PR plating of chromium.

Our work revealed that when the chromium deposit was made the anode it

dissolved with 100. percent efficiency as hexavalent chromium. At plating

voltage the reverse current was 2 to 3 times greater. The results of anodic
-2-

current-potential tests by Dr. Bertocci of this laboratory are shown in

Figure 1

This disparity in efficiency between the forward and reverse parts

of the PR cycle necessitated a reduction in current or time or both to at

least one-sixth of that for the forward part of the cycle. It was found

that short PR cycles of less than one minute total duration which are

effective in the cyanide baths could not be effectively used especially

in the dilute chromium baths because of poor distribution and the dark

and rough deposits obtained for most short cycle combinations tried.

Cycles longer than three minutes including a reverse portion long enough

to be effective in improving distribution caused removal of lead peroxide

from the anode and the formation of lead chroma te which built up in the

bath as a sludge and interfered with the efficiency of deposition and the

formation of a smootfi deposit.

Most of the PR cycles tried within the limits of the conditions outlined above resulted in chromium deposits with no better or poorer distribution than that obtained without PR. In this report data is given

on those cycles and conditions giving the best results, for the most part,

and that might have practical use. The obvious goal of the experiments

is to obtain a thickness ratio of one. Therefore, the success of any

particular test may be judged by how close the ratios are to this figure

in comparison to the best ratios obtained without PR.

The addition of certain chemicals to the chromium bath improved deposit

distribution botn with and without PR. Additives tried with some success

included oxalic acid, boric acid, and sodium hydroxide. The more dilute

chromium plating baths containing 100 or 250 g/1 of CrO^ gave slightly better

distribution on the test panels than more concentrated solutions. Also,

the additives were more effective in the dilute solutions with and without

PR.
-3-

The anticipated poor adhesion between chromium layers formed during

PR plating did not occur. It was therefore not necessary to use special

techniques such as slow build-up of the current before each forward part

of the cycle. In fact, no layering was visible in cross-sections of the

deposits until points of very high current density were examined such as

.chromium deposited using PR on the tops of threads.

The use of PR, dilute chromium plating solutions and additives to

the plating solutions Individually and collectively resulted in improved

edge to center distribution of chromium deposited on the flat test specimens used. PR cycles used most successfully, consisted of from 1 to 9

seconds reverse current depending on forward time and the amount of

reverse current. Forward times of from 50 to 180 seconds gave the most

consistent good results with 120 seconds perhaps the most effective.

Reverse currents from one-half to double or triple the forward current

but with equal ajiipere seconds were effective. Equal or higher reverse

current was effective with low forward current and short cycles. Edge

to center thickness ratios of 1.0 or less were sometimes obtained under

several conditions whereas without PR or additives the ratio could be

6 or 8. No full bright deposits were obtained using PR. See Figure 3

for several 5EM pictures of the as-plated surface. Hardness values of

all PR deposits were one-fourth to one-third less than the 1000 to 1100

Knoop hardness number for bright, hard chromium.

A current supply was obtained and tests were made using a pulsed dc

current in several concentrations of the chromium bath. Pulse peak levels

and durations were varied as were base current levels and intervals

between pulses. Several average current density levels for the pulse

on-off cycle.and bath temperatures were tried.
-4-

The literature (see bibliography) indicates improved hardness, better distribution and improved brightness for chromium deposits plated using pulsed

current or PC. A slight improvement was realized in deposit distribution

and brightness under certain conditions of pulse ratios and bath concentration. Hardness was not improved, at least at a bath temperature of

65°C.

Equipment .

The experimental chromium plating baths were contained in a one liter

beaker immersed in a water bath containing a copper heating-cooling coil

through which steam or cold water could be passed to maintain the desired

plating bath temperature. This assembly was placed on a magnetic stirrer

used continuously during all plating runs to maintain a uniform temperature

and concentration throughout the plating bath. (See Figure 2.)

Both a filtered and an unfiltered full wave rectifier were tried as

a plating current source without any difference in results being observed.

Nearly all runs were made using the filtered power supply with the unfiltered source connected to the circuit when additional current or

voltage was needed for high current tests in dilute solution. The current

reversing solonoid switch was a standard 100 ampere unit that allowed

insertion of current controlling resistance in either the forward or reverse

portions of the current cycle. Duration of each phase of the cycle was

controlled by a tandem recycling timer made by the Industrial Timer

Corporation. For very high reverse (three or four times forward) currents

it was necessary to use a resistance in the forward part of the cycle.

It would have been possible to supply each phase of the PR cycle with

separate rectifiers but it was not done in these tests.

Thickness of the deposits was measured at the extreme edges and near
-5-

the center with a micrometer. Measurements by a Kocour thickness tester

were also made on the deposits plated with PR current but about 1/16 to

1/8 inch from the edge depending on edge build-up. This instrument uses

a sulfuric acid solution to dissolve the chromium electrolytical ly with

thickness proportional to time. It requires the seating of a rubber

grommet on the surface of the deposit to contain the electrolyte. Thickness and distribution was also checked on some specimens by sectioning,

mounting in plastic and microscopical examination. A scanning electron

microscope was used for inspecting the surface texture of a few of the

specimens.

Procedure.

The specimens used were mild steel panels about thirty mils thick

and three inches square. They were stopped off with insulating lacquer

on the side away from the anode. The only surface treatment was degreasing before applying the lacquer. The specimens were supported at

the center on a one-quarter inch diameter rod bent at a right angle at

one end. The specimen was secured with a nut and washers. All exposed

areas of the support were stopped off. The anode was a three-sixteenth's

inch thick lead sheet slightly larger in area than the specimen and was

drilled with about three one-quarter inch holes per square inch of surface.

A number of runs were made with the specimens at an angle of 30 to 35

degrees to the anode to increase deposit distribution differentials but

most tests were made with the electrodes parallel and separated by about

13/16 inch. This separation was maintained constant by a plastic spacer

which screwed onto the exposed end of the supporting rod and bore against

the anode surface. See Figure 2.

The specimens were treated before plating by a reverse current of
-6-

one to three minutes duration in the plating bath with an additional forward current treatment below plating level for pulse-plated panels only.

Those that were to be plated by PR current were first plated three to

five minutes with forward current only, before the PR was started.

After plating from one to two and one half hours depending on the current

density and PR cycle used, current was shut off at the end of a forward

cycle which gave better appearance of the deposit surface. The specimens

were rinsed in warm water and the stop-off peeled from the back. Micrometer measurements were made at the edges and near the center. Chromium

thickness was determined by subtracting the known thickness of the steel.

The coulometric thickness measurements were made on the PR plated panels

only, in accordance with the procedure for using the Kocour thickness

tester. The sulfuric acid electrolyte furnished by the instrument manufacturer was used. The ratio of edge to center distribution of the deposit

was obtained by averaging the thickness of two edges of the specimen and

dividing this by the thickness at the center. Ratios for both coulometric

and micrometer measurements were calculated and included in the data for

PR deposits; micrometer data only, for PC deposits.

Deposits that were to be measured for hardness and for examination

were sectioned at the mid-point of one edge for a distance of about three

fourths inch toward the center. These approximately one fourth inch

wide sections were mounted on edge in bakelite in a standard mounting press.

The plating solutions were all made up with technical grade chromic

acid and with sulfuric acid as the catalyst at a chromic-sulfuric acid

ratio of one hundred to one. Solutions were used for several runs each

by maintaining the desired chromic acid concentration. Runs were made

for comparison without PR in the various bath concentrations and compositions
-7-

tried and at the various plating conditions. The 532 tests were necessarily

of an exploratory nature and complete series were not necessarily made of

each variable if it did not look promising. This method of testing makes

absolute comparison between variables not always possible but allows

broader coverage of the enormous number of possibilities with limited

finances and time.

Experimental Results with PR .

Cycle-time length tests.

Initial experiments showed much less differential between edge and

center deposit thickness than expected using parallel electrodes so the

first group of PR tests were made with the cathode at an angle of 30-35

degrees to the anode to accentuate distribution disparity. The closest

edge was one-fourth inch from the anode.

The first tests using PR used varying cycle times to try and determine

the most beneficial cycle length and proportion of forward time to reverse

time. It was found that the forward cycle had to be more than six times

longer than the reverse cycle or no deposit was formed. The dissolution

efficiency during the reverse was about six times that of the plating

efficiency during the forward part of the cycle. For most conditions

the effective cycle (the resultant forward current-time total per cycle)

had to be in the order of ten to twenty times the reverse total to obtain

coverage of the specimen by the deposit.

Short forward times of much less than sixty seconds resulted in dark,

matte deposits while longer forward times up to 180 seconds gave a lighter,

smoother deposit although the effective cycle was the same. This can in

part be attributed to the fact that all runs were stopped at the end of

the forward time and a longer period under normal bright plating conditions
-8-

resulted. But the improved appearance was greater than this effect could

account for. It may be that the longer cycles allowed more uniform dissolution of the plated surface rather than just enlarging the everpresent

channels and cracks as the short reverse times may do. It could also be

related to the time required to form a uniform cathode film or layer.

The cycles checked varied from six to 180 seconds forward and onefourth to ten second reverse. Those cycles that gave a deposit distribution ratio (coulometric measurement) of less than two on the angled

cathode in the 200 g/1 Cr02 bath were:

For. -Rev. Time Eff. Cyc.

18-1/8 sec.

60-1

180-1

asd For. -Rev. Surface

96-1

20-1

60-1

+20,-30

+20,-60

+20,-54

Matte

Satin

Semi-bri te

Edge to Ctr.

Thick.

1 .9 ratio

1.7

1.9

The average ratio was 3.3 for non-PR deposits at 20 A/dm2(asd) and range from

2.2 to 6. A test of cycle lengths in the 500 g/1 CrO^ bath with parallel

electrodes and at reverse current levels one-half forward current resulted

in ratios averaging 1.4. The cycles giving ratios of 1.3 or less were:

60-6 sec. 20-1 eff. Cyc. +30-15 asd Satin 1.3

90-13.5 13-1 1.1

90-9 20-1 , " 1.3

90-4.5 . 40-1 1.2

120-12 20-1 1.2

120-6 40-1 1.3

120-3 80-1 1.3

180-18 20-1 1.2

180-9 40-1 1.3

180-4,5 80-1 1.3

150-15 20-1 1.3
-9-

Two runs at 30 asd without PR had an average ratio of 2.3. As mentioned

earlier, runs with forward times of less than 60 sec. and effective ratios

less than 10-1 result in poor quality deposits and runs with reverse times

of more than about 20 sec. caused anode sludging.

A review of the overall performance of the cycles used at various

current densities with and without additives in the bath throughout this

investigation showed several that resulted in ratios of 1.3 or less more

consistently than when no PR was used. The following indicates the most

likely level of reverse current and the percentage of all the tests for

which a 1.3 or better ratio resulted:

No PR 44%

180-9 sec. 86 equal reverse (to forward current)

60-3 70 equal reverse

120-3 68 high reverse

180-6 63 equal or high reverse

120-6 63 low or equal reverse

60-1 1/2 60 high reverse

Bath Concentration .

The initial test of the effect of the concentration of chromic acid

in the bath was made with the cathode at an angle to the anode. Concentrations of 300, 400, and 500 g/1 CrO^ were tried. Ratios obtained from

this test were not optimum because of the short cycle times used. At

the time the test was run, the effect of cycle length v;as not fully

appreciated. The comparative performance for a more or less similar range

of cycles and plating conditions at each bath concentration is shown below.

The best average distribution (coulometric) is indicated as one.
-10-

300 g/1 Cr03 - 0.45

400 - 1.2

500 - 1.9

Performance for several series of test with a parallel cathode under

conditions that are comparable to the above data and calculated the same

way was:

100 g/1 Cr03 - 0.45

250 - 0. 45

500 - 0. 62

Data for a few tests selected for similar plating conditions for the 500

and 100 g/1 CrO^ baths are shown below

PR Cycle Effective Cycle

(sec)

CD

(asd)

Thickness

100 Cr03

Kocour Micrometer

Ratio

500 CrOg

K M

none 50 1 .2 1.5 1.8 4.3

30 1.3 1.9 2.8 7.3

II 20 1 .5 2.9 1.6 5.2

120-1 40-1 +30-90 1 .3 1.7 1.6 5.7

120-6 . " +30-15 1.3 2.7 1.3 6.5

40-4 (45-4.5) " •

. +50-25 1.8 1.8 1.8 7.5

60-6 (90-9) 20-1 II 1 .3 1.4 1.7 6.8

60-3 (60-4) " (15-1) +30-30 1.4 2.1 1 .3 3.1

Note: Parentheses indicate differences in1 cycle for 500 g/1 bath.

These tests of bath concentration showed that the more <dilute baths

gave substantially less edge build-up on flat specimens with and without

PR. Improvement in distribution by the use of PR is not evident in the

above detailed data for either the dilute or concentrated baths.

Figure 4 illustrates deposit thickness ratio differences induced by
-nbath concentration. Cross sections of deposits both with or without PR

show differences in thickness ratios resulting from bath concentration

as indicated in Figures 5 and 6.

Effect of Coating Back of Specimen .

A test was made to check the amount of edge and corner build-up and

the amount of coverage of the back area (facing away from the single

anode) by the chromium while using PR under various conditions. This

might give a better idea of differences in throwing power. The tests

were run in the 500 g/1 CrO^ bath.

The backs of the panels were completely covered with chromium when

no PR or the less sacrificial PR cycles were used. As might be expected

a less sacrificial PR cycle was required to eliminate bare areas on the

front of the panels with the backs uncoated than when coated, and the

deposit build-up at the extreme edges of the panel was diminished. However, improved deposit distribution over the entire front of the

panel was not realized. Some thickness ratios for conditions that resulted

in complete coverage of the front of the panels with uncoated backs compared to those with coated (c) backs follow:

PR Cycle Effective Cycle CD Surface Thickness

Ratio

No PR (c) +30 (asd) semi-bri te 1.8

No PR II 1 ight matte 1.5

60-1 (c) 30-1 II 1 ight matte 1.5

60-1 II II satin 1.0

90-1 (c) 45-1 II light matte 1 .5

90-1 11 II satin 0.9

90-2 (c) 22-1 II light matte 1.5

90-2 20-1 II satin 1.1
-12-

PR Effective Cycle .CD Surface Thickness

Ratio

180-4 (c) 23-1 " Satin 1.7

180-4 22-1 " " 1.3

180-6 (c) 15-1 " " 1.3

180-6 " " " 0.9

45-1 (c) 22-1 " " 1.4

45-1 " " light matte 1 .4

Average ratios were 1.2 for uncoated and 1.5 for coated specimens.

The difference between the averages 1.2 and 1.5 is about the same as between

the sample with no PR, 1.5 and 1 .8, indicati ng that the benefit of PR is

about the same in each case. The tests were made in the 500 g/1 CrO^

bath.

An interesting side effect of the plating of panels with uncoated

backs was the formation of rainbow colored oxides in areas of current

density too low for deposition of chromium. It presumably formed

during the reverse part of the cycle. This oxide coating was fairly

durable and the colors persistant.

Current Density Tests .

A determination of the effect of several plating current densities

on PR chromium distributions was made in the 500 g/1 CrO^ bath. A range

of PR cycles were checked for each current density. All deposits on each

average were made with short reverse times and high reverse cd. The following

is a summary of the ratios obtained for each current value:

20 asd forward current 1.6 coulometric 2.2 micrometer

30 1.5 3.4

40 1.4 5.1

50' 1.5 4.4
-13-

The distribution over most of the panel is apparently not adversely affected

by an increase in the forward current density. There is more build-up at

the extreme edges (micrometer measurement) at the higher forward current

density than at 30 asd and below. Figure 7 shows the coulometric ratios

at the current densities tried.

In other tests in the dilute (100 g/1 CrO^) and the standard (250

g/1 CrO^) plating baths, forward current densities considerably higher

were tried. A summary of the results follows:

75 asd forward current Std. soln.* 1.2 coulometric 1.8 micro

100 asd forward current Dilute soln.** 1.0

ICQ asd No PR " 1.2

100 asd No PR Std. soln. 1 .3

100 asd forward current " 1.4

150 asd forward current " 1.3

150 asd forward current Std soln.* 1.2

150 asd No PR " 1 .3

*Plus 20 g/1 NaOH

1.4

1.5

5.0

2.0

2.8

1.9

1.9

**Plus NaCl

It appears that edge build-up in the standard bath is greatly reduced

by PR but evaluating the effectiveness of PR at the very high forward

current densities is difficult because of nodule and dendrite formation

at the edges.' These growths protect the edge area from excessive buildup during plating and then are removed during rinsing or are too fragile

to contribute to the edge thickness measurement. So a panel that actually

had considerable build-up at the edges in these forms may appear better

in the measured thickness than those with actually better distribution.

However, later tests on screw threads indicated that these high current

densities would be of limited use on irregularly shaped work.
-14-

Reverse Current Level Tests .

Several panels were plated to find the most effective reverse current

level and forward current level combination for use in PR plating. Various

current densities were tried from one-half the forward current value to

over five times the forward current. The ratios for low reverse current

in the 500 g/1 CrO^ bath averaged 1.2 for the longer cycles and 1.7 for

the shorter cycles. Ratios for deposits made during these tests without

PR averaged 1.9. Some of the conditions including low reverse current

that gave the better deposit ratios were as follows:

180-36 sec. 10-1 eff. eye. +30-15 asd 1 ight matte 0.7

180-30 12-1 ' II satin 1.2

180-24 15-1 II II 1.3

60-12 10-1 II II 1.0

22.5-2 22-1 II matte 1.4

22.5-5 10-1 II dark satin 1.3

10-1/2 40-1 II II 1.4

10-1/4 80-1 +40^' 20 II 1.4

10-1 20-1 II matte 1.4

Several tests at 20 asd and at low reverse conditions resulted in bare

areas on the specimen even at effective cycles as high as 40-1 . The same

conditions gave continuous deposits at higher current densities.

The average ratio was 1.4 for equal reverse current in the 500 g/1

CrO^ bath. Two-thirds of the deposits did not completely cover the panel

at the low effective cycles used, 15-1 or less. About one-half of the

panels plated at similar conditions but with low reverse current did not

completely cover. Some of the conditions giving good results with equal

reverse current were:
-15-

120-12 sec. 10-1 eff. eye. +30-30 asd satin surface 1.3 ratio

60-4 15-1 " light rr.atte 1 .3

180-18 lOJ satin 1 .4

120-3 40-1 " light matte 1.3

60-3 20-1 " dark matte 1 .4

40-2 " +50-50 matte 1.3

60-3 " " satin' 1.3

120-3 40-1 "• " 1.3

180-9 20-1 " " 1.1

The tests shown above that are below the line were run in a 100 g/1 CrO^

bath. The average ratio was 1.3 for the tests in this dilute bath. PR

with equal reverse gives distribution ratios equivalent to those obtained

by low reverse current under the proper plating conditions and is more

efficient as less resistance is needed in the circuit for controlling

the current during the reverse period.

The high current reverse tests, of course, used shorter reverse

times to obtain the desired effective cycle. They were run in the 500

g/1 CrO^ bath. The average thickness ratio was 2.0 for these tests.

Figure 8 shows the average thickness ratios for all fully covered panels

at three levels of reverse current. Some of the more favorable conditions

for use with a high reverse current are shown below:

180-9 sec. 9-1 eff. eye. +30-68 asd satin surface 1.1 ratio

180-2 12-1 +30-50 " 1.3

60-1/3 40-1 " light matte 1 .4

60-1 11-1 +30-165 matte 1.2

120-2 12-1 " light matte 1 .3

120-2 20-1 +50-150 satin 1.4
Good distribution can be obtained with high reverse current but the higher

average ratio for the test indicates that the conditions required are

somewhat more critical than at lower reverse current levels. These higher

reverse current conditions can be used for plating PR in a chromium bath

without adding resistance to the circuit and are thus the most efficient

(electrically) and easiest to set up for. The reverse time would have to

be adjusted according to the reverse current obtained on a particular

piece of work being plated. Thereby the effective cycle giving the best

distribution of the deposit could be obtained. It may also be noted that

the effective cycles were slightly lower for the high reverse current

resulting in a lower average plating rate efficiency requiring a little

longer time to plate a given thickness of chromium.

Additives in the Chromium Bath used for PR plating

Oxalic Acid

A series of tests were made after adding a number of chemicals not

normally a part of the composition of a chromium bath. The first tried

was oxalic acid in amounts from 5 to 20 g/1 added to the 500 g/1 CrO^

bath. The main effect of the oxalic acid addition was an improvement

in the appearance of the PR deposits. The chromium was lighter and more

reflective.

Oxalic acid forms trivalent chromium in the normal hexavalent

+3

solution in roughly the proportion of one part Cr for two parts oxalic

+3

acid. The Cr thus formed is most likely the effective agent in improving

PR deposits. However, the amount of hexavalent chromium in the bath is

proportionately reduced. Increasing oxalic acid concentration did not

+3

result in improvement beyond the normal limits of maximum Cr concentration

in a bath before standard chromium deposits start to deteriorate as to

brightness a'nd hardness.
-17-

Additions of oxalic acid had to be made periodically to maintain the

Cr^^ as the Cr'^^ became oxidized at the anode. Controlling anode size

could avoid additions. The results would indicate improved appearance

when using PR for plating chromium on inside surfaces where anode area

+

is restricted and Cr •=> concentrations are usually higher.

Figure 9 shows the effect of oxalic addition to the 500 g/1 CrO^ bath.

Average thickness ratios for the tests run in the 500 g/1 CrO^ bath are:

1.44 for 5 g/1 oxalic acid, 1.37 for 10 g/1 and 1.25 for 20 g/1. Three

runs without PR with 10 g/1 oxalic acid had an average ratio of 1.5.

Some of the conditions selected from the te^t data resulting in good

chromium distribution are shown below:

5 g/1 Oxalic Acid

+40-60 asd

+50-150

+30-30

+30-15

10 g/1 Oxalic Acid

+30-30

120-1/2

120-1

120-2

120-6

60-1 eff. eye.

40-1

60-1

40-1

satin surface

matte

satin

satin

120-3

120-2

60-1

60-1

45-1

120-2

60-1/2

120-6

120-2

60-1

40-1

60-1

satin

satin

+40-120

15-1

20-1

20-1

+50-100

+30-15

20 g/1 Oxalic Acid

+30-90 satin

1 .3 ratio

1.1

1 .3

1.2

1.3

1 .2

1.2

1.1

1 .3

1.3

1 .2

1 .2

1 .3

1 .2
-18-

60-1 20-1 +30-90 satin 1.1

30-4 15-1 +50-25 " 1.3

40-4 20-1 " satin 1.1

Oxalic acid v;as also added to the dilute 100 g/1 CrO^ bath. The

average ratio was 1.2 for three runs with PR but without oxalic in this

bath. After the addition of 10 g/1 oxalic acid the average ratio was 1.1

for eleven runs. The first two runs in the bath had a ratio of less than

one which is one of the few times during this investigation that a

reversal of the normal distribution characteristics of chromium deposits

was achieved. Data on a few runs with 10 g/1 oxalic acid in the dilute

bath that had the best ratios are shown below:

120-6 sec. 40-1 eff. eye. +50-25 asd satin surface 0.9 ratio

40-4 20-1 " light matte 1 .1

120-12 "

' : +30-15 light matte 1.1

120-6 40-1 +50-25 satin 1.1

120-6 40-1 " semi- brt. 1.0

Under the above conditions a rather mild (slightly sacrificial) PR cycle

resulted in excellent distribution. The principle effect of the addition

of oxalic acid to a chromium bath used with PR seems to be in brightening

and smoothing the generally dull PR deposit but did result in slightly

better deposit distribution than any of the other experiments.

Boric Acid .

Boric acid was also tried as an additive at several concentrations

to the 100 and 250 g/1 CrO^ baths. Although the appearance of the deposits

was improved, little general improvement in deposit distribution was noted.

Average thickness ratios for PR deposits made with various boric acid concentrations in the dilute bath were: 1.4 for 5 g/1, 1.3 for 10 g/1, 1.35
-19-

for 20 g/1, 1.3 for 50 g/1, and 1.9 for 100 g/1. These data may be compared with those in the table under bath concentration. In the standard

250 g/1 CrO^ bath the ratio was 1.35 for 50 g/1 H^BO^. The standard

bath without addition or PR yielded a thickness ratio of 1.8 at 30 asd

and 1.4 at 50 asd. Additions of boric acid without PR gave ratios of 1.3

and 1.5 for dilute and standard baths respectively. Figures 10 and 11

show effects of boric acid additions.

Sodium Hydroxide .

Sodium hydroxide was added to the 250 g/1 CrO^ bath resulting in

somewhat improved deposit distribution with and without PR. Concentration of this additive was limited to less than 50 g/1 because of burning

and flaking of the chromium on the high current edges of the panels.

The current density range of deposition was apparently greatly reduced.

Appearance of the deposit was not adversely affected by adding up to

25 g/1 NaOH to the bath. Average deposition distribution ratios for NaOH

additions to the 250 g/1 CrO^ bath are: 1.5 for 10 g/1 and 1.4 for 25

g/1. The effect of NaOH additions on thickness ratios is shown in Figures

12 and 13. The addition of 25 g/1 NaOH resulted in non-plated edges in

the dilute bath but did not have this effect in the standard bath. That the

allowable amount of added NaOH is proportional to the CrO^ concentration

is demonstrated by the non-plated edges obtained when 25 g/1 NaOH was added

to a dilute bath. The edge effect was thought to be related to passivation

of the steel panel. Some of the conditions found to give good results when

using NaOH as an additive in the 250 g/1 CrO^ bath v/ere:

60-6 sec. 20-1 eff. eye. +50-25 asd satin surface 1.2 ratio

120-6 40-1 "

60-6 " " " 1.2

No PR ' — +30 . bright 1.2

+50 " 1.3
-20-

In the 100 g/1 CrO^ bath the average thickness ratio was 1.2 with

10 9/1 NaOH added using PR and 1.3 without PR. No PR and no NaOH gave

1.4. Some of the plating conditions tried which resulted in the best

thickness ratios are shown below:

120-6 sec. 20-1 eff. eye. +50-50 asd light matte surface 1.1 ratio

60-3 " " matte 1.1

180-4 1/2 40-1 " brt. satin 1.2

120-3 " " satin 1.2

40-1 " " matte 1.2

60-1/2 . " - " light matte 1.2

60-6 20-1 +50-25 matte 1.2

180-9 - " +50-50 satin 1.2

Consistently good results were obtained using PR cycles ranging from

40-1 sec to 180-12 sec. Several runs without PR had an average ratio of 1.3

at 30 and 50 asd. Deposit distribution ratio was 1.4 for several runs in

the dilute bath with no additive or PR. The effects of NaOH addition on

the deposit is shown in Figure 14.

Sodium Chloride .

Another sodium compound, sodium chloride, was tried as a leveling

additive in the chromium bath. It was used in the dilute (100 g/1 CrO^)

bath in amounts from 5 to 30 g/1. At the highest concentration it caused

burnt or bare edges on the panel in four out of five tests. Most of the

tests were run at 50 asd and with three runs at 100 asd. A summary of

the NaCl concentrations and the resulting thickness distribution ratios

is shown in Figure 13 and below:

5 g/1 NaCl 1.3 ave. ratio 1.2 median ratio -r,

10 1.2 1.2
-21-

15 g/1 NaCl 1.2 ave. ratio 1.1 median ratio

20 1.0

30 1.2 1.2

No deposition or burning occurred on the extreme edges of the panel

even without PR. Some chlorine gas was released at the anode and the

effect of an addition of NaCl decreased after a few runs. Such conditions

would probably make the addition of NaCl to the chromium bath of limited

use.

Sodium Carbonate .

A few tests were made of the benefits of adding sodium carbonate

for improving the distribution of chromium. The results were not as good

as for some of the other additives tried. For tests using 10 to 20 g/1

of NaCO^ in the dilute CrO^ bath the average and median ratio was 1.3.

Summary of Additives .

An overall comparison of the coulometric (c) and micrometer (M)

thickness data obtained using additives in the CrO^ bath on the basis

of current densities used is given below:

Deposit Thickness Ratios

of CI. 5 and M3.5 or less CI. 3 and M3.0 or less

Oxalic acid at 30 asd 70% 30%

(cone. & Dil . bath) 40 asd 83 50

50 74 53

Boric Acid at 30 87.5 50

(dil . & std. bath) 50 100 80

Sodium hydroxide at 30 55 29

(dil . & std. bath) 50 93 79

Sodium Chloride at 50 100 82

(dil. bath) . 100 100 100

Sodium Carbonate 50 89 56
-22-

Bath Temperature and Deposit Appearance .

A series of runs were made in the dilute (100 g/1 CrO^) bath at 30

asd with all conditions including the PR cycle the same except that the

temperature was varied from 35 to 90°C. The temperature resulting in

the best appearance - smoothest and brightest deposit - was 65° with

60 and 70° nearly as good. This temperature is only about 10-15° higher

than normally used in chromium plating and it would seem practical to

make PR deposits at this temperature for the benefit of improved appearance.

The 65° temperature did not give the best distribution of the deposit

at the PR cycle used (120-3 sec) so a series of PR cycles was tried at

the same conditions to find a combination that would result in improved

distribution as well as improved appearance. Several PR cycles at 20 asd

did not result in the desired low thickness ratios but at 50 asd most of

the PR cycles tried resulted in ratios of 1.3 or better. Several of the

better combinations at 65°C giving good surface appearance are detailed

below:

High Reverse Current

120-1 1/2 sec. 40-1 eff. eye. +50-100 asd semi-brt. surface 1.3 ratio

20-1 " 120-3 ,

120-4

120-12

120-16

120-24

120-6

60-3

20-2

15-1

20-1

15-1

10-1

40-1

II

20-1

Low Reverse

+50-25

brt . satin 1 .1

satin 1.3

satin 1 .1

satin 1.3

1 .3

brt. satin 1.2

satin 1 .3

light matte 1 .2
-23-

Equal Reverse

20-1/2 sec. 40-1 eff. eye. 50-50 asd matte 1.2 ratio

40-1 " " light matte 1 .3

60-1 1/2 " " " 1.2

180-4 1/2 " " brt. satin 1.1

60-3 20-1 - " satin 1.1

40-2 " " light matte 1 .3

The average deposit distribution ratio for this series at 50 asd was 1.4,

The average ratio of 1.5 was obtained for similar runs at 55°C.

Cross-Section of PR Deposits .

The hardness of a number of deposits was made on the cross-section

using a microhardness machine with a Knoop indenter and a 200 g load.

The deposits were sectioned and mounted in bakelite to make the measurements. An indication of the edge build-up or thickness ratio was also

obtained from photographs of the cross-sections at the edge and edge +

1.5 cm. Some of these pictures are included at the end of this report.

PR deposits and deposits plated using bath additives without PR

showed some decrease in hardness over standard bright chromium deposits

but most retained considerable hardness as shown in the data below.

These data indicate that PR deposits would be hard enough for most

applications of chromium.

(edge-edge +1 .5

No PR dilute bath 50 asd 1077 KHN200 2.5 ratio

No PR dilute bath 30 1006 2.3

No PR dilute bath " 983 1.7

No PR dilute bath 20 934 2.7

No PR 10 g/1 oxalic acid 30 777 3.4

No PR 20 g/1 boric acid " 797 1 .6

No PR 30 g/1 boric acid " 999 1.6
-24-

(edge-edge +1.5 cm)

No PR 25 g/1 IMaOH 30 asd 947 KHN200 1 .3

No PR 25 a/1 NaOH 50 1037 1 6

60-1 sec. dilute bath + boric+30-90 781 3.1

120-2 std. bath + NaOH II 693 2.4

60-1 1/2 dilute bath II 469 6.0

60-1 dilute bath II 824 2.4

120-1 dilute bath II 723 2.1

60-3 dilute bath +30-30 812 2.2

120-3 oxalic acid addn. II 589 6.0

120-6 oxalic acid addn. 30-15 / 700 4.7

120-6 dilute + oxalic II 969 1.6

120-6 boric acid addn. II 638 1.6

120-6 NaOH addn. II 973 2.0

120-6 dilute bath II 983 1.3

60-6 dilute bath 30-15 743 2.0

120-6 dilute bath II 664 2.6

40-4 dilute bath II 756 1.8

iplified comparison is given by averages of the hardness data •

No PR - 1000 KHN200

No PR plus addn. - 911

PR - high reverse - 698

PR - equal reverse - 701

PR - low reverse - 803

From the standpoint of hardness it appears that a low PR reverse current

is preferable and the thickness ratios are also good.

Combination of Favorable Conditions .

There WBre several plating conditions or bath modifications that
-25-

seemed to improve chromium distribution or appearance. A few tests were

made combining several of these favorable conditions in hopes that tliey

were additive and thus produce the best possible chromium deposit. The

tests were made in a dilute (100 g/1 CrO^) bath with the addition of

10 g/1 NaOH and used reverse current equal to or lower than the forward

current at 50 asd and 65°C. The deposits were all satin or better in

appearance and had deposit thickness ratios of 1.3 or better but only

one had a deposit ratio of 1.0 which was obtained with a PR cycle of

120-6 sec, effective cycle of 20-1 and equal reverse current. A control

deposit plated without PR had a ratio of 1.3 but the extreme edge buildup was slightly higher than for any of the runs with PR.

Screw Threads Plated with Best PR Conditions .

A number of l/4"-20 screw threads were plated with chromium in the

dilute (100 g/1 CrO^) bath and in the standard (250 g/1 CrO^) bath. Best

current and PR conditions for obtaining uniform deposit distribution on

a panel were not necessarily best for threads. Reverse currents higher

than about 65 asd resulted in poorer distribution than without PR. Cycles

that were too sacrificial, larger proportion of reverse time and current

to forward time and current, resulted in no deposit in the bottom of the

grooves of the threads. A forward current density of 50 asd with PR worked

well on panels but currents of 30 or 20 asd worked better on threads. It

may have been that gasing in the thread grooves increased resistance

of the solution in this critical area more or less in proportion to the

current density. With virtually no gas involved during reverse, the

benefits of PR were reduced. Only additions of NaOH were tried during

these runs and it improved distribution without the use of PR in the

standard bath and gave some advantage with PR in the dilute bath.
-26-

Despite the factors working against good deposit distribution, thickness ratios between the top and bottom of the threads in the 250 g/1

bath were reduced from a low of 2.7 without PR to 1.3 with PR at similar

bath conditions. About the same or poorer distribution is obtained from

an electroless nickel bath without special agitation of the solution.

Some of the conditions giving relatively good results on the threads

were:

Dilute + NaOH 55°C 120-3 sec. 20-1 eff. eye. +50-100 asd 2.3 ratio

" " "

" +30-60 2.

120-6 4'0-l +30-15 2.

" . " "" +20-10 1 .5

, " " 120-9 25-1 +30-15 2.5

" 65°C 120-12 20-1 +50-25 2.5

Std. Bath " 120-3 " +30-60 1.3

" V"

, 120-6 " +30-30 2.

" 120-5 " +50-65 2.

Std. + NaOH " 120-3 " +30-60 1 .3

" . : " ; No PR — +30 3.

" " No PR — +50 5.

The average of all seven deposits without PR was 3.5.

The results of plating the threads in comparison to the results on

the panels indicate that it may be necessary to adjust the PR cycle to

the type of contour being chromium plated to obtain the most uniform

deposit distribution. Also the standard (250 g/1 CrO^) chromium bath

(average ratio 3.3) seems to work as well or better than the dilute

(100 g/1 CrO^) bath (average ratio 3.7) when plating threads. This is

not necessarily true for panels. Photographs of several cross-sections

of the threads are included as Figure 15.
-27-

Summary of PR Chromium Plating Tests .

Some of the factors involved in PR chromium plating which were made

evident during these tests are listed below:

1. Reverse current efficiency is about six times plating efficiency.

2. Chromium is dissolved from the cathode in the hexavalent state.

3. Periodic reversal of the current for periods of less than 30

seconds has no detectable adverse effect on the continuity of

the deposit at normal current densities.

4. The reverse portion of the PR cycle produces 2-3 times the

plating current at plating voltag^.

5. The PR cycle that gave the lowest ratios was 120-6 sec. with

reverse current one-half plating current in the dilute bath

plus oxalic acid.

6. Short sacrificial PR cycles yielded dark matte deposits but

usually better uniformity of thickness under most bath conditions .

7. Smoothness and brightness of PR deposits may be improved by

plating at end of run for a few minutes without reversing.

8. PR cycles longer than three minutes cause sludging of the anode

especially in concentrated CrO^ solutions because of the amount

of reverse current necessary for thickness ratio improvement.

9. The higher current density regularly used (50 asd) gave best

distribution on flat panels with and without PR.

10. Reverse currents that were higher than 4 times forward current

with effective cycles of 15-1 or less tended to dissolve so

much chromium from low current density areas that poorer distribution or even bare areas resulted.
-28-

n. Addition of up to 25 g/1 of oxalic acid, boric acid or sodium

hydroxide improves appearance of PR deposits, distribution of

standard deposits and PR deposits with oxalic acid.

12. Rainbow colored oxides form on steel areas below plating current

density during PR plating in CrO^ bath.

13. The range of hardness of PR deposits is less than that of

standard bright chromium.

14. Appearance and distribution of PR chromium improved by increasing

the level or Cr^^ in CrO^ bath, e.g. by the addition of oxalic

acid to the bath.

15. Conditions giving improved deposit distribution with PR chromium

not necessarily additive.

16. Threads may be plated with PR chromium with a thickness ratio

of only 1 .3

Equipment for Pulsed Current Tests.

A current supply that produced millisecond pulses of dc current was

obtained from Rapid Electric Company. The unit had five controls, two of

which were timers with which pulse-time off could be controlled within

0-100 ms. A rehostat adjusted the pulse voltage, another adjusted the

percentage of the pulse voltage desired for the base current or fraction

of the pulse voltage to be applied to the work between pulses. A third

rehostat limited the pulse current provided it was set for a current less

than that delivered by the voltage setting. The shape of some pulse

wave forms are shown in Figure 16. A Tektronix type 51 3A oscilloscope

was used to monitor the wave form of the pulse. This could be connected

to either the voltage or current output of the pulser. The remainder

of the plating set-up was the same as for PR plating with heavy, well

spaced leads used to supply current to the work for minimizing induction.
-29-

Experimental Results with PC .

Pulse time and level tests

Initial tests in the 250 g/1 CrO^ bath indicated that at both 30

and 45 amperes per square decimeter and at 65°C there was some improvement in the distribution of the chromium deposit on the 3x3 inch flat

polished steel panels at certain pulse conditions. It was also discovered

that the base setting of current between pulses must be above 20 percent

of the pulse voltage to obtain at least a satin surface on the chromium

deposit. A test, described later, indicated that the uncertainty of

deposit distribution reproducibility was about 18%. It was found at this

time that a reverse current of 1 to 3 minutes before plating did not give

adequate adhesion at the edges when plating with a pulse of more than 30 asd.

A forward current below plating level for one minute after a one minute

reverse solved the adhesion problem.

Pulse time variables at 55 and 65°C

A series of tests were made with varying pulse-on and pulse-off

times at 65°C and 45 asd in the 250 g/1 bath using a 25% base setting

between pulses. Current density as measured by the meter is an average

of pulse and base current. Pulse current increased as pulse time and

base level decreased and as time between pulses increased. Two pulse

conditions, 10 ms. on - 30 ms. off and 2 ms. on - 2 ms. off gave edge

to center thickness ratios of 1.7 and 1.9 respectively as measured with

a micrometer. Two tests without pulsing at the same conditions yielded

thickness ratios of 2.3. At 65°C both of the above low ratio deposits had

a matte surface. Poorest ratio was 2.4 at 50-10 ms. At 55°C and 45

asd the best ratios of 2.0 were obtained at 30-30 and 10-10 ms., the

poorest of 2.4 at 3-2 and 5-5 ms. The deposits were dull.
-30-

Base voltage

In addition to a base voltage of 35% of pulse voltage for betweenpulse current setting, several other base levels were tried. The literature

(listed in the bibliography at the end of this report) recommended one

third pulse voltage for the base setting for chromium plating. A number

of tests were made at 33% of pulse voltage and at several pulse-times.

A number of tests were also run with the pulse-time at 7 asd on and

21 asd off with only the base setting varied. All tests were run

in the 250 g/1 CrO^ bath at 55°C and 45 asd. At 75% base setting the

best thickness ratio of 1.4 and plating efficiency of 14.4% was obtained.

A later confirmatory test gave a ratio of 1.9 and efficiency of 14.0%.

At 60% base setting the ratio was 1.7 and plating efficiency 13.0%. All

three deposits were bright. This test indicates that the relatively

high base settings of 60 to 75% yielded the best results at least at the

plating condition used. A tabulation of the data is shown below.

Base Setting Surface Efficiency Cr Thickness Ratio

pulse edge-center

33% semi -bright 9.8% 2.3

n II 6.9 2.0

40 near-bright 8.1 1.8

II bright 9.7 2.0

45 II 9.5 2.4

50 II 12.3 2.4

- II semi -bright 11 .9 2.4

60 bri ght 13.0 1.7

75 II 14.4 1.4

II II 14.0 1.9

Figure 17 is ci plot of plating efficiency versus base voltage settings.
-31-

Hardness tests of PC deposits

Cross-sections were made of several deposits plated with a range

of pulse ratios and at 65°C/45 asd in the 250 g/1 CrO-^ bath. There was

little relation between the surface appearance of the deposits and the

hardness. Two bright deposits had a hardness of about 600 and 700 KHN200

respectively and two matte deposits measured about 875 KHN200' the

average the longer cycles of 30-30 and 50-50 ms. resulted in the harder

deposits. Shorter cycles of 2-2, 10-10, and 10-30 ms. gave the softest

deposits with a low of 357 KHN2oo- Individual measurements are shown

below:

Pulse Temp/CD Hardness

(ms) (KHN200)

50-50 65/60 835

65-45 692

" " 876

30-30 " 875

.

10-10 " 595

.1 II 323

10-30 " 357

2-2 "

' 449

Pulse ratio tests

Further exploration of pulse on-pulse off time ratios were made at

55°C/45 asd at base voltage settings of 33 and 50% of pulse voltage.

Confirmation of the results of improved surface appearance at higher

base settings was obtained. Ten of the 24 deposits made at 33% base

voltage setting v/ere matte while none of those made at 50% were matte.

The poorest surface at the latter setting was a bright satin and most

were semi -bright or bright. Twenty-one deposits were made at 50% base
-32-

setting with an average thickness ratio of 2.1 while the average of twentyfour made at 33% was 2.4 although there were more low (1„8 or less) thickness ratios at the 33% base setting. For example, a pulse time of 20-60

ms. gave a thickness ratio of 1.6. The best thickness ratio at 50% base

setting was 1.7 obtained at 10-5 and 15-15 ms. pulse times. A pulse-time

ratio of 1 on to 3 off showed evidence of being preferable. A test at

25% base setting and 10-10, 10-20, 10-30 ms. pulse timing gave thickness

ratios of 2.3, 2.2, and 1.7 respectively. While some other pulse times

such as 50-50 ms. and 10-5 ms. gave occasional good results pulse-time

ratios with pulse times greater or equal to off-time generally gave

poorer chromium distribution.

Duplication of low ratio deposits

A number of panels were plated at conditions that duplicated previous tests resulting in better than normal deposit distribution with

ratios from 1.8 to 1.4. In most cases only one duplicate was made at

each set of conditions and the thickness ratios ran a little higher than

the original results in most cases. However, only four of the fourteen

deposits had ratios greater than 18% higher than initial deposits and

most were less than 12% higher in this test. Pulse times for these

low thickness ratios obtained at 55°C/45 asd in the 250 g/1 CrO^ bath

ranged from 3-15 through 15-15 and 7-21 to 25-75 ms. A deposit plated

with conventional dc at the same conditions had a thickness ratio of 2.5.

Dilute chromium plating bath

The effect of a dilute 100 g/1 CrO^ bath with PC was investigated.

As in the PR tests, improvement in deposit distribution was realized in

the dilute bath. Also, nearly all the PC deposits were bright. The

usual complaint about plating in the dilute CrO^ bath is the limited

bright range.
-33-

Nine runs were m^de in the dilute bath and a range of pulse times

and base voltage settings were used. All deposits had a thickness ratio

of 1.8 or less with one panel having a nearly uniform thickness with a

'

ratio of 0.9o The ratios of the five best panels averaged 1.3. A deposit

plated with standard dc current had a thickness ratio of 1.6. Detailed

data for the test are shown below:

Pulse

on-off

16-49 ms.

25-100

15-15

10-5

3-15

50-50

7-21

10-30

100-0

Base Setting

(% pulse)

33%

11

50

II

33

II

75'

25

Temp. /CD

(°C/asd)

55/45

Surface

nr .-brt

.

bright

It. matte

bright

Efficiency Cr Thickness

Ratio

65-45

55/45

nr. brt.

bright

12.7%

11.8

13.7

12.2

9.7

12.4

13.4

7.0

14.9

Edge-ctr.

1.4

1.3

1.8

1.3

0.9

1.2

1.2

1.5

1.6

Concentrated chromium plating bath

Eight runs in a 500 g/1 CrO^ bath gave just the opposite results of

those obtained in the dilute bath. Most deposits were matte and deposit

thickness ratios were high. However, all deposit thickness ratios with

pulsed current were considerably lower than the 7.4 ratio obtained using

standard dc current. The best ratio obtained in the concentrated bath was

1.6 for a 10-30 ms. pulse at a 25% base setting. The average thickness

ratio for aeposits made with pulsed current was 3.4. All tests were made

at 55°C/45 asd.

Current controlled pulse

Most of the runs made with pulsed current utilized the voltage control
-34-

to maintain the desired average current and the current control was set

to allow the maximum current to flow. A few tests were made with the

voltage control at maximum and average current was maintained with the

current control rehostat. No appreciable difference was noted in

deposit distribution from the 250 g/1 CrO^ bath at 55°C/45 asd. There

was some indication that the appearance might be slightly improved as

all the deposits were bright but many deposits from this bath were

bright wnen voltage control of the average current was used.

Summary of PC Chromium Plating Tests .

Some of the findings made during the PC tests in the chromium plating

bath that might be of more general interest are given below:

1. Distribution of the chromium deposit was improved at some

conditions of pulsed current.

2. Pulsed current has no observed deleterious effect on chromium

properties, except a possible reduction in hardness, and may

improve the brightness at some conditions of deposition and

bath composition.

3. Efficiency of deposition was about normal for many pulse-on,

pulse-off time ratios but poorer for some than when using

standard dc current.

4. Contacts to work should be secure to prevent arcing during

high current peak pulses and leads sized and arranged to minimize induction due to high frequency pulsing.

5. Appearance of deposits made with pulsed current is as good or

better than those made with regular dc in the standard (250 g/1)

or dilute (100 g/1) bath and average much better than those

made with PR current.
-35-

6. The concentration of CrO^ in the bath had a pronounced effect

on the deposit distribution and appearance when using PC although

there was some improvement in uniformity over regular dc current

at all concentrations.

7. Improvements in deposit uniformity and appearance were experienced over a wide range of pulse on-off ratios and base voltage

settings

.

8. There was some indication that certain pulse ratios and base

settings were more effective at certain bath concentrations,

e.g. the base setting of 33% and pulse ratio of 3-15 ms.

that gave a 0.9 thickness ratio in the dilute bath.

9. No brightening of initially dull surfaces was experienced when

using pulsed current for chromium plating.

10. Plating rates were changed by changes in the pulse duration and

pulse on-off ratios even for the same average current, e.g. in the

concentrated bath at 45 asd a 10-5 pulse for 2 hrs. gave 2.3 mils

of Cr, a 25-100 pulse 1.6 mils for a respective efficiency of

12.2 and 8.5%.

Conclusions .

Both PR and PC power supplies resulted in somewhat improved distribution

of chromium deposits from a wide variety of bath concentrations and currenttime conditions. PR current always resulted in deposits that were less bright

or smooth on the surface than standard dc. PC improved the appearance of

the deposit in baths of low concentration (250 g/1 or less). Hardness of

the chromium deposits was reduced by both types of power supplies with

the greatest reduction by PR although in most cases the hardness still

would be effective for wear resistance and greater than that for chromium
-36-

heated to 600°C. Plating rates varied with the PR or PC time schedule

used but no rates were greater than normal for standard dc current. PR

+3 seems to be more effective with higher than normal limits of Cr (trivalent) in tne bath and might be useful for plating tube bores.
BIBLIOGRAPHY

1. Avila, A.J. and Brown, M.J., Design Factors in Pulse Plating ,

Plating 57, 1105 (1970).

2. Bakhvalov, G.T., New Technology of Electrodeposition of Metals :

Current Reversal in Electroplating (Russian), Metallurgiya

Publishing House, Moscow (1966).

3. Bayens, P., Trans. Inst. Metal Fin. 31, 429 (1954).

4. Bedi, R., High-Speed Chromium Plating , Metal Fin. 69_, 9, (1967).

5. Burrus, C.A., Pulse Plating of High Resistance Materials, etc. ,

J. Electrochem. Soc. IjS^, 833 (1971 ).

6. Cheh, H.Y., Electrodeposition of Gold by Pulsed Current , J. Electrochem. Soc. 118, 551 and 1132 (1971).

7. Combs, Eugene L., Chromium Plating Speed Tables , Plating 39, 482,

May (1952).

8. Dana, P. and Linford, H.B., Cleaning and Preparation of Metals

Prior to Electroplating , Plating 55^, 5, 456 (1968).

9. Davies, G.R., Effect of Current Source on the Properties of Chromium

Electroplate , Trans. Inst. Metal Fin. 51, part 2, (1973) pp. 47-55.

10. Dini, J.W., Periodic Reverse Plating , Met. Fin. 61, 7, (1963).

11. Faust, C.L. et al.. Electroplating Chromium Directly on Aluminum,

Plating 48, 6, 605 (1961).

12. Gerber, E., PR Chromium , Metal laberflache, 6, 11, B161 (1954).

13. Gerber, Von E., Periodic Reverse Current , Metallaberflache, Vol. 6,

No. 11 (1954).

14. Hausner, J.K., Methods of Electrodepositing Chromium , U.S. Patent

2,852,447.

15. Hausner, J.R., Apparatus with Power Source for Plating , U.S. Patent

3,616,434.

16. Hickling, A. and Rothbaum, H.P., Cyclic Electrolysis: Part I, II ;

The Influence of Periodic Reversal of Current Upon the Surface

Roughness of Electrodeposited Copper , Trans. Inst. Met. Fin. 34_,

(1956-1957), pp. 53 and 199.

17. Jernstedt, G.H., Better Deposits at Greater Speeds by PR Plating,

Plating 35_, 708 (1948), July.

18. Jernstedt, G.W. and Patrick, J.D., Long Cycle PR Plating , U.S.

Patent 2,678,909.

19. Kakovkina, V.G. et al , Effect of the Form of Current on the Quality

of Chromium Deposits , Politekh. Inst. im. V.I. Lenina, Ser. Khim.

Tadshnol 18, 5, 107-15 (1958).

20. Krishnan, R.M., High-Speed Chromium Plating , Met. Fin. 69, 9 (1971).

21. Kruglikov, S.S. et al , The Influence of Periodic Interruptions of

Current on the Electrodeposition of Nickel from Leveling Solutions ,

Plating 53, 1 , 78 (1966).

22. Lamb, V.A., Electroplating with Current Pulses in the Microsecond

Range , Plating 56, 8 (1969) 909-13.

23. Ogburn, F., Salmon, H.; Commutator for Periodically Changing the

Direction and Magnitude of Direct Currents , Plating 43, 2 (1956).

24. Pamfilov, A.I. et al. Chrome Plating with Asymmetric Alternating

Current , Ukrainskiy Khimicheskiy Zhurnal, Russian, Vol. 26, No, 1,

(1960), pp. 31-5.,

25. Pinkerton, H. et al , PR Copper Cyanide Plating of Printed Wiring

Boards , Plating 59, 7, 672 (1972).

26. Read, H.J.; Hall, R.H.; and Pinkerton, H.L., Current Reversal Devices

for PR Plating in the Laboratory, Plating 35, 1222 (1948) December.

27. Saddington, J., Hoey, G.; Crack-free Chromium from Conventional

Plating Baths , 65th Tech. Conf. AES (1974).
28. Safranek, W.H. and Miller, H.R., Acid Zinc Deposition , U.S. Patents

2,905,603 and 3,005,759.

29. Schaer, G.R., Power Supply for Chromium Plating , U.S. Patents

3,111,479 and 3,042,592.

30. Slizhis, R., Electrodeposi tion of Metals , Proc. 10th Lithuanian

Conf. Electrochem., Pub. for NBS, 26 (1970).

31. Smith, R.C., A Study of Growth Processes in Germanium Dendrites

using Pulse Electroplating Techniques , J. Electrochem. Soc.

108 , 238 (1961).

32. Snavely, C.A., The Mechanism of Chromium Plating , Trans. Electrochem. Soc. 92, 537 (1947).

33. Spencer, L.F., Developments in Chromium Plating , Met. Fin. 59_,

12 (1961).

34. Stromatt, R.W. and Lindquist, J.R., Invention Rept. - Pulsed Current

Electroplating , February 1966, 4 p. NASA 25 03 No. 04741.

35. Tedeschi, R.J., Plating Automation with Solid State Rectifiers and

Controls , Metal Finishing 11, 49 (1971).

36. Tvarnsko, A., A 100 Ampere Motor-Driven Rotating Contact Unit ,

Plating 6£, 8 (1973).

37. Wan, C. et al. The Application of Pulsed Plating Techniques to

Metal Deposition I, A Critical Review of the Literature , Plating 61_,

6, 559 (1974).

38. Winenger, Cyclic Plating of Hard Chromium on Turbine Rotor ,

Journals - MRAES 33, 617 (1946) June.

39. Zhikh, V.A., More Efficient Chromium Plating by Current Reversal ,

Russian Engineering Journal, No. 7, 56-8, 1972, 10B353, (Vestn.

Mashin.)
CO

i_

O)>

sE

E

O

S- J=o

14-o

3

o

o

%.

4-> O

'a;

o

4-

to

I I

J ^I ^1

I I

Plastic

PanelSpacer

Lead

Anode

c

Stirrer

Plastic Cover

Figure 2. Electrode and bath arrangement for experimental PR plating

b c

Figure 3. SEi'i photographs of the as-plated chromium surfaces: a) PR 120-3 sec,

50720 ascU effective cycle 80-1, satin surface; b) PR 120-1 sec, 50730 asd,

effective cycle 40-1, matte surface, c) PR 120-1 sec plus 5 g/1 oxalic acid

in bath, 50°/30 asd, effective cycle 40-1, semi-bright surface, llOOX

Figure 4. CrO-s bath concentration using angled and parallel cathodes.





o> +-> I— J3

>^n +-> o •r- i_ c

cr

c/J s-> c

O)

s_S-u

01 o

UO

00 c

s_ •«- CU 4-> > «o

0) 1—

CO

CU

CO o&. o r ' 1 O

cn ooIT)

O

CM oCO 1 CM Zl o

CM

00 CM

+->

(/) O • CL tf\ OJ CU -O

-t-> cs: -r- Q. (/> c o -o O 4Jc

(/) OJ too>

<U 4-» CD fO

03

a; 4-i > ro

C3>

)

-T - S — - -V

-J.-.-:

,1

—:—V

—, -> 4

1,.

J 5^ ; v - ; >,--'-

_-j ^ —z:v

O

C\J

CD O03

ro OS- ooo4-» •o

0) -a • a cn

(O c

•r— <D +-> •a fo

>< Q. o

-O Q-o E

Z3

•1- ^ -O 4J O 03

CM

LO CO

1^^

L

cn

rtr o

-.( , -_- , , . O I o I

CO • EO C

r- "n4-> 4-> •r- 03 -a r—

•O Q.

OS

(1) a. XJ

•I- s_

s- o o 4- O JC

4-> E <0 3 XI

T3 OO O OlO S- O -aC I—

03 '-^ cn •o o •r- OX I— oO 4J >> fO -C s_

fO E Q. 3 <U

•r- CO o o

CO 4->

CO

CO CM

^^^^^^^ 1 41 J o

cn

CM

4-o

4-» • •1- TD

ID

-O n3

ra

O '—in

-Q—

LO

•-> un O ^ SZ 4-> +J 03

•r- Jli 3 CO

-a oc i.

<^

— cn ^ o -P LO

•r- CJo+J CM

td-I «DCM

CO

=tfe

cn

Q.

O

>

to oCO

o

IT)

XJ

T3o

o

CDE

f3 to LO -o

(O

SI ••^ 4J Oro S --^

<L) IT) S-O

CO O I GJ O

fO I— O) Q.I—U

S- >i o u

4- QJ O >

•r— to -M C O

O O)

•I- 4-

4-> 4-

CJ CD

<UCO O

CO CO o

O I oCM

CD

s13

LO CD

CD X

r- O

(J i.

>

u

(D

<+- 4-

GJ m f— o! s_ O C_J

C\Ja C71 a

(/) oun

in CNj

I o c

-o <:

Figure 16. Pulse wave forms at (top) 50/i base, A5s.sd.; (center) 25% base, A5asd; (bottom)

25%'bbEe, 30asd. 10 ra— sec on, 10 off. Center piilse cvirrent controlled, otiaers

voltage controlled.

>)Uc

<u

4—o

•MT3

(1) 4->

Qi

CJ) fO i-

+-> ^~ to • o ro > S—O

CJto

rfO o > 4-> O.

<+—

C QJ o 0) -r— S- r— 3 a.

cn

O fO c

•r— a> +->

+-> 00 c

+J to 0)

OJ ja sto

OJ lO o

CO

fO '3 <1> Q3 Q. cn 1 ro C iO) OJ

0) > 2 CO . +-> <D «+- DO 0

<u

s.3

Test PR Cycle Effective Forward Cr Cr Thickness Ratio

No. (sec.) Cycle Current Surface (mil) (Edge to Edge)

for. -rev. (sec) Density Near Edge Center Far Edge

(asd)

13 12-1/2 8-1 20 Dk. -partly bare 0.10 0.03 0 - 14 fi II It Matte 0.45 0.14 0.009 • 5^0

15 none - II Dull 0.10 0.02 0.015 - 19 It - II Satin 1.45 0.S9 0.50 2.9

20 It - 11 Semi -brite 1.16 0.52 0.52 2.2

21 12-1/2 • 8-1 It Dk. -matte- 0.14 0.06 -0.04 3.5

22 12-1/4 24-1 II Matte 0.27 0.10 0.06 4.5

23 It 27-1 II It 0.39 0.10 0.06 6.5

24 It It II tt

* 0.32 0.09 0.05 6.4

25 II 24-1 II Dk. -matte 1.03 0.17 0.09 11.5

26 none II Semi -brite 1.81 0.37 0.30 6

27 12-1/2 8-1 II 0 0 • 0

28* 18-1/2 12-1 II Satin 1.89 0.22 0.17 11.1

29 It II II Matte 0.24 0.14 0.06 4

30 18-1/4 27-1 II Matte 0.90 0.45 0.36 2.5

31 ti 24-1 II It 1.63 0.56 0.33 4.9

32 18-1/8 96-1" ii» It 1.66 0.83 0.87 1.9

33 none •I Brite 1.46 0.49 0.47 3.1

34 18-1/8 96-1 II Matte 1.32 0.59 0.53 2.5

35 24-1/8 128-1 It II 1.36 0.67 0.61 2.2

• 36 12-1/8 70-1 30 II 1.49 0.79 0.28 5.3

37 •1 II •1 II 1.28 0.39 0.23 5.6

38 30-1 11-1 20 It 1.50 0.13 0.01 150

. 39*** It 10-1 II Dk . -matte 1.40 0.18 0.11 12.7

40 60-1 20-1 II Satin 1.25 0.78 0.72 1.7

41 120-1 42-1 II It 1.64 0.85 0.61 2.7

42 90-1 32-1 It It 1.64 0.78 0.77 2.1

43 180-1 60-1 II Semi -brite 1.40 0.72 0.73 1.9

44 none II Brite 1.77 0.72 0.61 2.9

45 22.5-1/8 90-1 II It 1.93 0.70 0.66 2.9

46 180-2 35-1 •1 Satin 1.77 0.68 0.65 2.7

PR not working last 1/2 hr of plating time.

Based on current differential between forward and reverse parts of cycle as shown on rectifier meter.

***New bath.

Test

No.

47

4849

SO

SI

S2S3

S4

SS

S657

5859

60

61

62

63

646566

676869

70

71

7273

74

757677

7879* 80

8182

83

14

8586

87

88

89

90

9192

PR Cycle

For. -Rev.

(sec)

18C-3

180-4 180-S

lSO-5

180-6

180-8 180-10

90-5

90-4 4S-2

22.S-1 45-3

60-3

60-2 43-2

45-3

45-3

45-4 45-4

22.5-1. 22.5-1 45-3

45-2

5-1

3

45

224545-3

45-3 60-3

60-3

90-3 45-2

45-2 60-3

60-3

45-2

60-2

90-2

45-1 45-1.5

45-1.

S

45-1,5

45-2

22.5-1

22.5-1 22.5-1

Effective Cycle

22-1

17-1

13-1

11-1 8- 1 6.5-1

H9- 1 8- 1 9- 1 5.5-1

8- 1 11-1

9-1

S.S-1

6-1 4-1

4-1

5.5-1

8-1 5.5-1

8-1

8rl

ff s.s-/

n

n7-1m

ii-i

8-1 9-1 7-1

7-1

9-1 11-1 15-1 16-1 11.5-1

12- 1 10.5-1 //«-l

Forward Current Density

(asd)

Cr

Surface Cr Thickness

(mil)

Edge Center Edge

Thickness

Ratio

Cycle Variation Tests

20 Satin 1.50 0.51 0.56 2.7

1.50 0.59 0.54 2.8

Platte 1.30 0.48 0.48 2.7 Satin 1.85 0.57 0.58 3.2

1.41 0.40 0.49 2.9

M Matte* 1.43 0.29 0.23 6.2

If •f • 1.20 0.27 0.24 5.0

n If • 0.73 0.33 0.28 2.6

n If • 1.98 O.SO 0.38 S.2 n ft 1.50 0.38 0.40 3.8

n ft • 0.41

n «

• 1.14 . n * If • 1.43 0.36 0.31 4.6

n ft 1.19 0.44

• 0.43 2.8

•t It 1.12 0.48 0.52 2.2

Concentration Tests (300 g/1)

20 Matte* 0.95 0.26 3.6

0.12 0.06 0.06 2.0

0.37 - 0.13 2.8

If

ft 0.73 2.8

It Matte* 0.59

It n

• 0.94 .

It ft 1.39 0.32 0.25 S.S

"400 g/1 CrOj r

20 Matte 0.64 0.23 0.27 2.4

ft . It 1.20 0.24 0.37 3.3

ft ft * 0.03

It

ftn Matte* 1.06 n II 0.82

ft ft • 0.45 0.18 0.11 4.1

ft ft 1.05

ft ft * 1.09 0.22 0.17 6.4

ft ft • 0.53

500 g/1 CrOj

20

ft

•

" •

ft Matte* 0.60

ft ft 0.56 0.19 0.17 3.3

N ft 0.95 0.23 0.17 S.S

ff ft • 0.60

30 0.96

0.97

1.25 1.13

1.51 0.51

0.21 0.36

0.30

0.06

0.36

0.34

0.13

0.11

0.07

0.08

7.4

8.8

16

6.4

Parallel Cathode and Anode (500 g/1 CrOj)

93 45-2 30 Matte* 0.30 0.36 0.27 0.8

94 45-2 n ft ff • 0.47 0.44 0.25 -I.

I

95 ft Semi-Brt 1.12 0.58 0.92 1.9

96 45-1 J2W-1 ft Matte 1.22 0.57 0.92 2.1

97 60-1 .9<?48-l ft It 0.91 0.61 0.96 1.5

98 90-1 »5"0-l ft Lt. Matte 1.01 0.67 1.35 2.0

99 90-2 aa-iS-i n II 0.86 0.56 0.60 l.S

100 180-4 ft Satin 0.84 0.50 0.67 1.7

101 180-6 ft ft 0.70 0.55 0.69 1.3

102 180-8 ft fa 0.56 0.41 0.32 1.4

^^Unplated area on specimen

Based on current differential between forward and reverse parts of cycle as shown on rectifier meter at the „,same voltage settin; . ^ Bath filtered to remove fine sludge, -eostly lead chromat".

Test PR Cycle Effective Forward Cr Cr Thickness

No. For. -Rev. Cycle Current Surface (oil)

(sec) ' Density

(asd) Edge-Ctr.(K) Ratio Edge-Ctr. (M) Ratio

Specimen with back coated (CI and imcoated .

95 fCI none 30 w\^ UiX w 4 W 1 .12-0.58 1 .

8

3.8-0.8 A 7 103 II Mb* UuakkC 1 .40-0 . 92 1 .

5

7.5-2.2

116 22.S-1 10-1 II Matte* 0.43-0. S3 0.8 0,8-0.

7

1 1 X . 1 lis 60-1/2 SO-1 H Satin 0 64-0 fiO 1 .

1

1.2-0.6 7 ft 60-1 30-1 tf 0,91-0.ol 1.5 3 . 0-1 .

0

T 0 114 II ft II Satin 0 67-0 fi^ X1 . 0u 7 1 113 60-2 15-1 II It 0.54-0.46 1 .

2

1 .5-0,5 3.

0

98so fCI v.k-j 90-1 45-1 II Lt matt«* 1 .01-0.67 1 .5 5 . 7-1 .

1

3 4 111 »i *J — X

11 0 6'^-0 6R - 0.9 1 J,_ft 7 7 0 99 fn 90-2 77-1— X

If Lab • uki LLC nU. R6-n 0(J— u * oo 1X.J 0 . 9-1 •

X

J . ^

fi 70iU 1 —

X

II Sat in X . X

1 c n A 7 c

1lUUon m^V* J 180-4 — J-X fl •1 1 7 "toil 7 7 106 If 77 1 *l ft nU A*^-0 sj. • *tO — U • 0*+ 1.0 1 X 7 7 0 fl 7 7

1 01 fn 180-6 1^-1 iO-X ff ft 0.70-0 .55 1 . J J . U— X •

X

7 7

1 (1^ It It It It ft T7 n TO 1 7 0 A 7 ft 1 n9 fr'\ lOU -o XX— 11 1

X

II ft U • 9D -U • *t i X

1

. A4 ^

7 . 0U—0U . 7

/

7 Q

1 fiA 11 fl tl u • OJ - u

.

vJ . ^

1 0 0 fl X . 0 27 1 -1 If Plat uc nU . 6"^ O.J — nU AdD*+ ^ ,1 X . U Q T 0 7 7 A 117 , II If fl tl • 0.73-0.81 0.9 0.8-0.7 1.1 129(C) 45-1 22-1 If Satin 0.94-0.69 1.4 4.6-1.1 4.2

118 ft • t tf Lt. matte 1.21-0. SS 1.4 6.4-1.2 5.3 119 45-2 11-1 ff 11 * 0.78-0.80 1.0 1.7-0.8 2.1 128 (C) 60-1 30-1 ft Satin 1.12-0.95 1.2 4.0-1.

1

3.6

122 It If ft tf • 0 '5^-0 '^n 0.7 0 3-0 5 0 f< 121 60-2 15-1 fl ft 0U.^U— 56-0U.JOfi 1.0 . 1.0-0.8 I 2 120 60-3 ' 12-1 It Lt. matte* U.JU—U.JO 0.3 0.3-0.4 0.8

130(C) 90-2 23-1 tf Satin 0.71-0.40 1.8 3.2-0.5 6.4

124 90-3 15-1 If II 0.63-0.72 0.9 2.0-1.0 2.0

123 90-4.5 10-1 It If 0 82-0 78 1 .

1

2.6-1.4 1 .9 127 120-2 30-1 It tf 1.40-0.73 1.9 1.3-1 .

2

1 .

1

126 120-4 15-1 If It 0.9 1X • 1X .1-X 1

X

1 .0 125 120-6 10-1 XW—

X

It ft 0.53-0.47 1X.J^ u • 0— u

0

0 A

Current Density Test I J u u 5/1 ^ ^ J

140 22.3-1 8-1 20 (no Cr) - 141 45-1 15-1 If Satin 0.52-0.35 1.5 1.6-0.5 3.2

142 "•O 1 fcU —

i

It ft A A7-n XA 1 fl 7 4 0 7 X • 4 14^ OU— £• tf If n ^7-0 1 C 1.3 1X . 7/ —

ftU . 7/ 7

1

II tt If ft i • 0

1 n n £

X

1

• 7/

*J — X 77-1 30 Matte 1 77 n ^7 1

• X

t A ft A Q 7 94 45-2 11-1 II II 0.47-0-44 1.1 1.1-0.3 3.7

97 60-1 30-1 n Lt. matte 0.91-0,61 l.S 3.0-1.0 3.0

98 90-1 3 V—

X

*» J "A ft If X • UA —u 0

/

1 c t 7-1 1 J .

/ -X •

X

J . 4 99 90-2 22-1 ff Lt. matte n R6-n "^^^ 1 c X • w JT ^.1 1 • J—X .

X

JX . 7^ 100 180-4 ti n Satin u • 0*+ - u • X

1

• 7/ O.U-X toil

X

101 A VX 180-6 If II ft 7ft-n X • w 0toil . U-X • X

7 7 102 180-8 11-1 tf If ft 56-0 41 1.4 2.0-0.7 2.9

133 22.5-1 11-1 40 Matte 0.63-0.64 1.0 5.3-0.7 7.6

129 45-1 22-1 If Satin 0.94-0.69 1.4 4.6-1.1 4.2

128 60-1 30-1 It If 1.12-0. 95 1.2 4.0-1.1 3.6

130 90-2 22-1 ff ft 0.71-0.40 1.8 3.2-0.5 6.4

131 180-6 15-1 If ft 1.06-0.65 1.6 3.2-1.7 3.1 132 180-8 11-1 If ft 0.67-0.54 1.2 4.0-0.7 5.7

134 22.S-1 U-1 50 Matte 0.61-0.43 1.4 2.4-2.2 1.1

135 4S-1 20-1 II Satin 0.99-0.87 1.1 3.7-0.8 4.0

136 60-1 2S-1 It II 1.55-0.90 1.7 S.9-1.2 4.9

138 60-2 13-1 ft II 1.42-0.92 1.5 S.6-0.8 7.0

137 90-2 20-1 tf ft 1.17-0.94 1.3 4.3-1.0 4.3

Unplated area on specimen

I. Based on current differential between forward and reverse parts of cycle as shown on rectifier meter at a given

voltage setting.

NOTE: All runs were made in a SOOg/1 CrOj bath with 100-1 sulfate. ^

K • Kocour thickness moasurenient

.

M Thickness measurcnent by niicrometer.

Test PR Cycle Effective For. -Rev. Cr Cr Thickness

No. Fox. -Rev. Cycle** Current Density Surface Edge-Ctr. (K) Edge-Ctr. (M) (sec.) (asd) Ratio Ratio

Current Density Test Cont.

138 60-2 13-1 50-116 Satin

139 60-2 20—60 Satin 1.5

140 22.5-1 7-1 20-60 No Cr 141 45-1 16-1 20-55 Satin Z.4 6.6

142 60-1 21-1 20—59 Satin 1.5 3.0

143 60-2 10-1 20-60 Satin 1.4 2.8

144 none 50- Brt 1.8 4.3

145 none 40- Semi-Brt 1.8 2.5

Concrolled Reverse Current .-

146 180-16 11-1 30-30 Satin 1.

5

2.2 147 120-12 10-1 30-30 Satin 1.3 5.8

148 90-9 10-1 30-30 Lt matte*

149 90-6 15-1 30-30 Lt matte* 1.1 5.3 150 90-9 10-1 30-30 Satin* 4.5

151 130-18 10-1 30-30 Satin* 1.8 6.4

152 60-4 15-1 30-30 Lc matte 1.3 3.1

153 60-6 10-1 30-30 Lt matte* 1.4 3.1

154 45-4 11-1 30-30 Lt matte* 1. 7 3.7 155 22.5-2 11-1 30-30 Matte* 1.5 2.3

156 11-1 11-1 30-30 Satin* 2.4 3.3 157 10-1 10-1 30-30 Matte* 3.1 4.3

158 180-18 10-1 30-30 Satin 1.4 2.5

Low Reverse Current

159 180-36 10-1 30-15 Lc matte 0.7 . 1.0

179 160-30 12-1 30-15 Satin 1.2 3.4 180 180-24 15-1 30-15 Satin 1.3 8.4

181 180-24 15-1 30-15 Satin 4.7

160 90-18 10-1 30-15 Satin X.5 2.2

161 60-12 10-1 30-15 Satin 1.0 4.8

162 45-9 10-1 30-15 L£ matte* 1.0 13.0

163 45-9 10-1 30-15 Matte* 1.0 4.5

164 60-12 10-1 30-15 Matte* . 1.4 10.0

165 none 30- Brt ° 2.8 7.3

166 30- Brt 1 fi

Cycle--Length Test

167 60-9 13-1 30-15 Satin 1.5 3.7

168 60-6 20-1 30-15 Satin 1.3 6.3

169 60-3 40-1 30-15 Satin 1.4 5.9 170 90-13.5 13-1 30-15 Satin l.X 4.9 171 90-9 20-1 30-15 Satin 1.3 4.8

172 90-4.5 40-1 30-15 Satin 1-2 4.1

173 120-12 20-1 30-15 Satin 1.2 6.6

Test PR Cycle Effective For. -Rev. Cr Cr Thickness

No. For. -Rev. Cycle** Current Density Surface Edge-Ctr. (K) Edge-Ctr. (M) (sec.) (asd) Ratio Ratio Cycle-Length Test Cont.

174 120-6 40-1 30-15 Satin 1.3 6.5

175 120-3 80-1 30-15 Satin 1.3 7.1

176 180-18 20-1 30-15 Satin 1.2 5.4 177 180-9 40-1 30-15 Satin 1.3 3.6

178 180-4.5 80-1 30-15 Satin 1.3 5.1

182 150-30 lC-1 30-15 Satin 1.7 5.3

183 150-22.5 13-1 30-15 Satin 2.8 7.3 184 150-15 20-1 30-15 Satin 1.3 3.4

High Current Reverse

185 90-4.5 10-1 30-60 Matte 2.0 3.2

186 90-3 13-1 30-68 Matte 1.6 2.2

187 180-9 9-1 30-68 Satin-*- 1.1 5.1 188 180-4.5 10-1 30-120 Lt Matte* 1.6 10.0

189 180-2 12-1 30-150 Satin 1.3 3.9 190 60-e.

J

40-1 30-150 Lt Matte 1.4 5.6

191 (0-1 11-1 30-165 Matte 1.2 1.9

* Unplatcd area on spociaon

** Based on current difference between forward and reverse parts of cycle.'

Note:

Test PR Cycle Effective Current Cr Cr Thickness Ratio

No. For. -Rev. Cycle** Density Surface Edge-Ctr. (K) Edge-Ctr. (M) (sec) For. -Rev. (mil)

(asd)

High Current Reverse (cont.)

194 60-2 6-1 30-165 Satin* 0.008-0 — —

195 120-2 12-1 30-165 Lt. Matte 0.58-0.46 1.3 3.0 196 120-1.5 16-1 30-165 Satin 0.66-0.45 1.5 7.7

228 120-2 15-1 20-85 No Cr

229 120-1 30-1 20-85 Cr at extm. Gdgss only

230 120-1 40-1 30-90 Matte 0.71-0.44 5.7 231 120-2 15-1 30-120 Satin* 0.39-0.15 2.6 —

232 120-2 15-1 40-160 Satin* 1.17-0.41 2.6 3.9 233 120-1 30-1 40-160 Matte 1.30-0.48 2.7 4.9

234 120-1/2 60-1 40-160 Matte 2.02-0. 70 2.9 4.7

235 120-1/2 120-1 50-100 Lt. Matte 2.25-0.73 3.1 4.0 236 120-1 60-1 50-100 Matte 1.86-0.70 2.7 4.3 237 120-2 30-1 • 50-100 Lt. Matte 2.21-0; 71 3.1 3.9 238 120-2 30-1 50-150 Matte 1.68-0.62 2.7 4.4

239 120-3 13-1 50-150 Satin 0.66-0.35 1.9 6.4

Low Current Reverse (Cont.)

197 45-4.5 20-1 • 30-15 . Lt. Matte 0.81-0.49 1.7 9.2

198 45-2 45-1 30-15 Lt. Matte 1.55-0.76 2.0 8.2

199 45-2 45-1 30-15 Satin 1.01-0.66 1.5 12.0

200 45-1 90-1 30-15 Satin 0.93-0.59 1.6 9.3

201 22.5-2 22-1 30-15 ^Matte 0.64-0.45 1.4 4.0

202 22.5-1 45-1 30-15 Satin 1.32-0.78 1.7 4.5

203 22.5-5 90-1 30-15 Dk. Satin 1.18-0.90 1.3 2.4 204 10-1 20-1 30-15 Dk. Satin 0.86-0.35 1.5 5.7 205 10-.

5

40-1 30-15 Dk. Satin 1.02-0.73 1.4 4.5

206 10-. 25 80-1 30-15 Dk. Satin 1.06-0.65 1.6 12.3

Test PR Cycle Effective Current Cr Cr Thickness Ratio

No. For.-Rev% Cycle** Density Surface Edge-Ctr . (K) Edge -Ctr.

(sec) For .-Rev. (mil)

(asd)

Low Current Reverse (Cont.)

207 10-. 25 80-1 40-20 Dk. Satin 0.75-0.55 1.4 5,0

208 10-.

5

40-1 40-20 Dk. Satin 1.58-0.84 1.9 5.0

209 10-1 20-1 40-20 Matte 0.91-0.67 1.4 6.3

210 22.5-2 20-1 40-20 Satin 0.63-0.33 1.9 4.3

211 10-2 10-1 40-20 (No Cr) 212 22-1 40-1 40-20 Satin 0.99-0.50 2.0 7.1

213 45-1 90-1 40-20 Satin 1.32-0.67 2.0 10.2

214 45-2 45-1- 40-20 Satin 0.76-0.48 1.6 9.0

215 45-4.5 20-1 40-20 Satin 0.85-0.48 1.8 7.5 216 45-9 10-1 40-20 Satin* 0.54-0.27 2.0 17.2

217 90-18 10-1 40-20 Satin* 0.35-0.25 1.3 10.0

218 120-24 10-1 40-20 Matte* 0.26-0.09 2.9 7.0

219 180-30 10-1 40-20 Satin* 0.52-0.23 2.3 18.0

220 90-9 20-1 40-20 Satin* 1.22-0.73 1.7 6.8

221 120-24 10-1 20-10 Satin* 0.006

222 120-12 20-1 20-10 Satin* 0.49-0.34 1.4 1.6

223 120-6 40-1 20-10 Satin* 0.73-0.40 1.8 7.3 224 No PR 20-10 Lt. Satin 0.68-0.44 1.5 6.0

225 120-3 80-1 20-10 Satin 0.52-0.31 1.7 2.0

226"^ 120-3 80-1 20-10 Satin 0.53-0.35 1.5 4.4

227 No PR Satin 0.74-0.47 1.6 5.2

Edge Mounted

240 120-3 13-1 50-150 Matte 0.66-0.32 2.1 8.3

241 120-4 10-1 50-150 Semi-brite 0.03-0.02 1.5 " 13.0

242 120-1 40-1 50-150 Matte 1.13-0.71 1.7 6.8

243 120-2 20-1 50-150 • Sntin O.B4-0.60 1.4 9.4

244 120-1 30-1 40-160 Satin 0.77-0.49 1.6 10.7

245 120-2 15-1 40-160 Satin 1.34-0.77 1.7 7.0

Test PR Cycle Effective Current Cr Cr Thickness Ratio

No. For.—Rev, Cycle** Density Surface Edge-Ctr. (K) Edge—Ctr.

(sec) For. -Rev. (mil)

(asd)

Plus 5 g/1 Oxalic Acid

2A6 120-1 40-1 30-90 Semi-brlte 0.84-0.60 1.4 5.2

247 120-1/2 60-1 40-160 Satin 0.94-0.73 1.3 7.3 248 120-2 15-1 40-160 Satin 0.83-0.44 1.9 8.1

249 120-2 20-1 50-150 Matte 1.08-0.74 1.5 4.0

250 120-1 40-1 50-150 Matte 1.27-1.18 1 1X 2 .

8

251 120-3 40-1 30-30 Satin 0.96-0.66 1.5 8.3

252 120-2 60-1 30-30 Satin 0.94-0.75 1.3 3.2

253 120-6 40-1 30-15 Satin 0.85-0.70 1.2 4.6

Plus 10 g/1 Oxalic Acid

254 120-6 40-1 30-15 Satin 1.01-0.73 1.4 2.9

255 120-3 40-1 30-30 Satin 0.94-0.72 1.3 2.5

256 120-2 60-1 30-30 Satin 1.22-0.99 - 1.2 4.5

257 No PR 30 Brt 1.41-1.04 1.4 , 4.8

• Unplated area on specimen

** Based on current difference between forward and reverse parts of cycle + New bath

Note: All runs niade in 500 g/1 CrO^ bath with 100-1 sulfate. K Kocour thickness measurement. M Micrometer measurement at extreme edges and central area of specimen.

Test FK Cycle Effective Current Cr , Cr Tlilckppss RaLlo

No. For.-Kuv. Cycle** Dun.sity Surf.ice Edye-Ctr (K) (M) (sec) For.-Kov. (mil)

(asd)

Plus 10 g/1 oxalic acid (cont.)

256+ No PR 50 Sacin 2.91-1.91 1.6 2.8

259 40 Brc 1.92-1.20 1.6 9.0 260+ 120-1 ^40-1 30-90 Scmt-Brt 1.33-0.92 1.4 4.7

261 II 1.66-0.82 2.0 3.1

262 '60-1 20-1 It Lt, Ilnttc 1.01-0.71 1.4 3.4 263+ fl II Satin 0.80-0.69 1.2 3.7 264+ II H II 0.90-0.54 1.8 1.7 265 11 II 40-120 1.13-1.04 1.1 3.1 266+ 1* It It 1.04-0.77 1.5 2.0 267+ 11 It H tt 0.80-0.49 1.6 7.6 268 45-1 15-1 tl 0.64-0.59 1.4 1.5 269+ tl 11 It 0.66-0. 50 1.3 1.6 270 120-2 20-1 II It 0.85-0.67 1.3 2.8 271+ 60-1.5 50-100 0.53-0.43 1.2 1.6

272 40-1 II 0.66-0.43 1.5 2.3 273+ 20-1 10-1 II No deposit

274 30-1 15-1 Satin* 0.42-0.32 1.3 5.5

275+ 30-4 15-1 50-25 Matte 0.58-0.50 1.1 7.1 276 40-4 20-1 0.82-0.58 1.4 4.1 277+ 120-6 40-1 0.92-0.66 1.4 2.0 278 It 30-15 0.76-0.63 1.2 1.8

Plus 20 g/1 oxalic acid

279+ 120-2 20-1 30-90 Satin 0.86-0.65 1.3 1.6 280 60-1 0.60-0.50 1.2 2.0 281 45-1 15-1 II ft 0.69-0.47 1.5 2.5 282 60-1 20-1 It tl 0.55-0.49 1.1 1.4

283+ 30-4 15-1 50-25

• 0.95-0.72 1.3 2.1 264 40-4 20-1 II tt 1.22-1.15 1.1 1.8

Dilute bath - 100 g/1 CrOj

285 30-4 15-1 50^25 No SO/, addition-No Cr 286 40-4 20-1 Lt. Katte 2.91-1.89 1.5 1.7

287 30-4 15-1 It 1.89-1.64 1.1 1.8

283 120-6 40-1 It Semi-brt 2.27-2.20 1.0 2.2

Dilute bath + 10 g/1 oxalic acid

289 120-6 40-1 50-25 Satin 2.14-2.33 0.9 1.7 290 30-4 15-1 tl Blk. 0.68-1.96 0.3 1.2 + Additions of oxalic acid

* Unplated area on specimen

Test PR Cycle Effective Current Cr' Cr Thickness Ratio

No. For. -Rev. Cycle** Density Surface Edge-Ctr (K) (M) (sec) For. -Rev. (mil)

(asd)

Dilute Bath (100 g/1 Cr03) + 10 g/1 Oxalic Acid

£7 1 20-1 50-25 L.L* 1 t- riaLi.c M;4tte 11 . <jO •3P_11 • c70u 1 11 4 292*+ 45-1 15-1 30-90 Black 0.68-0.37 2 !i 6 .4 293 60-1 20-1 II Matte 1.51-1.31 1 .2 2 .3 294*+ 120-2 N n Lt. Matte 2.27-1 .95 1 .3 1 .7 295 120-12 li 30-15 1.78-1.17 1 .5 1 .6 296 40-4 N 50-25 u fc.U/ 7 fi7-?t..*tJ I _ ]

1 _ 2 298 120-6 40-1 L 1 II 1 1 . 1 1

1

•5 ^ 286 40-4 • 20-1 M Lt. Matte • 2.91-1.89 1 .5 1 .7 287 30-4 15-1 n n 1.89-1.64 1 .2 1 .8 288 120-6 40-1 N Semi Brt 2.27-2.20 1 .0 2 .2

Dilute Bath + 5 g/1 Boric Acid

299* 120-6 40-1 30-15 Satin 2.27-1.36 1 .7 2 .5 300 120-12 20-1 11 1.96-1.31 1 .5 2 .7 301* 120-6 40-1 50-25 Brt. Satin 2.29-1.72 1 .3 1 .6 302 40-4 20-1 Lt. Matte ] _2 2 _2

10 g/1 Boric Acid

303* 120-6 40-1 50-25 Satin 1.89-1.47 1 .3 1 .6 304 40-4 20-1 11 Lt. Matte 1.87-1.51 1 .2 1 .8 305* 120-6 40-1 30-15 Satin 1.31-1.00 1 .3 2 .4

20 g/1 Boric Acid

306 120-6 40-1 30-15 Lt. Matte 1.48-1.17 1 .3 307 30- Brt 1.55-1.09 1 .4 3 .0

50 g/1 Boric Acid

308 50- Brt 2.14-1.82 1 .2 2 .0 309* 120-5 40-1 50-25 Brt. Satin 1.42-1.19 1 .2 1 .9 310 180-8 40-1 u 1.61-1.26 1 .3 1 .8 311 40-4 20-1 n Hatte 1.59-1.17 1 .4 1 .5

» 100 g/1 Boric Acid

312* 120-6 20-1 50-25 Lt. Matte 1.68-1.17 1 .4 1 .5 313 120-2 m 30-90 1.16-0.94 1 .2 1 .8 314 60-1 m Dk. Matte 1.56-0.50 3 .1 4 .4

250 g/1 Cr03, 50 g/1 Boric Acid

315 60-1 20-1 30-90 Matte 0.33-0 .23 1 .4 2.8

316 120-2 M Lt. Matte 1,18-0 .90 1 .3 2.7

317 120-6 40-1 50-25 II 2.11-1 .74 1.2 1.6 318 40-4 20-1 11 Hatte 2.45-1 .84 1 .3 2.6

319 50- Brt 1.59-1 .03 1.5 2.2 320* 120-12 20-1 50-25 Satin 1.78-1 .36 1.3 2.3

321 180-9 • 40-1 tl u 2.07-1 .75 1 .2 2.4

322 20- Brt 1.54-0 .98 1.6 4.1 323 60-2/3 20-1 50-100 Lt. Matte 1.69-1 .27 1.3 3.2 324 120-1-1/3 Satin 1.55-1 .07 1.4 2.4

325 120-2/3 40-1 n 2.59-1 .97 1.3 2.7

250 g/1 Cr03 Only No PR

326 50- Brt 2.62-1 .89 1.4 3.5 327 30- U 2.29-1 .28 1.8 3.4

* Make-up addn. of Cr03

+ Make-up addn. of Cxaiic Acid

Note: K=Kocour thickness neasurenent.

M=Microineter measurement at extreme edges and central area of specimen.

lest KK L/clu LtrtLlivf lurmnl Cr i.r IliicMirss KaLio

No. For. -Rev. Cycle" Uonsity Surface Ldqo-Ctr. (K) (M) (sec) For.-Kov. (mil)

(asd)

10 g/1 NaOH added to 250 g/1 CrO, Bath

328 30 Brt 2.03-1 .34 1.5 2.9

329 120-2 20-1 30-90 Satin 1 .85-1 .09 1 .7 2.8

330 60-1 Lt. Matte 1 .77-1 .05 1.7 1 .5 331 60-6 30-15 Satin 1 .65-1 .08 1 .5 3.0

332 50-25 2.25-1 .86 1.2 3.4

333 120-6 40-1 1 2.81-2.27 1 .2 2.7 334 II 30-15 H

1 .79-1 .22 1 .5 3.2

25 g/1 NaOH

335 120-6 40-1 30-15 Satin 1 .71-1 .10 1 .6 3.2

336 50-25 1.99-1.60 1.2 2.3

337 60-6 20-1 1 .67-1 .39 1 .2 2.4

333 II 30-15 Lt. Matte 1 .60-0.98 1 .6 3.4

339 II " 30-90 Matte 1 .69-1 .02 1.7 3.3

340 120-1 40-1 Satin 1 .44-1 .05 1 .4 1 .8 341 30 Brt 1 .82-1 .48 1 .2 2.0

342 50 3.02-2.30 1 .3 •

1 .8

50 g/1 NaOH

343 50 Brt* 2.57-2.04 1 .3 1 .6 344 --- --- 30 11+ 1.65-1 .51 1.1 1.6

345 20 11+

1 .41-1 .19 1 .2 1.1 346 120-1 40-1 30-90 Matte* 1.56-1.21 1.3 1.1 347 60-1 20-1 2.30-1 .51 1 .5 1 .4 348 60-6 30-15 II +

1 .59-0.85 1 .9 1.7

349 120-6 40-1 II +

1 .85-1 .16 1 .6 1 .3 350 50-25 Satin* 2.79-1 .86 1.5 2.1

351 60-6 20-1 Matte^ 3.03-2.13 1 .4 1 .2 352 40-4 2.39-1.29 1.9 1.7

100 g/1 CrO^ Bath-(no additive)

353 — — 30 .Brt 2.12-1.65 1.3 1..9 354 20 1 .50-1 .02 1 .5 2.9

355 50 3.32-2.77 1.2 1 .5 356 120-6 10-1 50-25 Satin 3.19-2.08 1.5 2.4

357* 60-6 20-1 2.46-1.92 1.3 1 !4 358 40-4 2.71-1.49 1 .8 1 .8 359 120-1.5 40-1 30-60 Brt Satin 1.90-1.12 1.7 1.7 360 60-1.5 20-1 Dk. Matte 1.21-0.69 1.8 2.6 361* 60-1 30-90 Matte 1 .97-1 .53 1.3 2.1

Test PR Cycle Effective Current Cr Cr Thickness Ratio

No. For. -Rev Cycle** Densi ty Surface Edge-Ctr. (K) (M) (sec) For. -Rev (mil)

(asd)

362 60-6 20-1 30-15 Blk 1. 74-0.69 2 .5 3 0 363* 120-6 40-1 Satin 1. 25-0 94 1 .3 2 7 364 40-4 20-1 61k 0. 55-0 21 2 .5 5 8 365 120-1 40-1 30-90 Satin 2. 10-1.65 1 .3 1 7

Forward + Reverse Current Equal (100 g/l Cr03)

366* 120-3 40-1 30-30 Lt. Matte 2. 29-1 82 1 .3 1 8 367 50-3 20-1 Ok. Matte 1. 71-1 24 1 .4 2 1 368 40-2 Blk 0 23-0 15 1 .5 4 8 369 50-50 Matte 2. 63-2 03 1 .3 1 8 370 60-3 Satin 2. 67-2 08 1 .3 1 8 371* 120-3 40-1 2. 52-2 02 1 .3 1 5 372 180-9 . 20-1 2.47-2 20 1 .1 1 1

Temperature Test (100 g/l Cr03)

373* 120-3 40-1 (45°) 30-30 Lt. Matte 1 74-1 04 1 .7 2 3

374 (40°) Matte 2 48-1 89 1 .3 2 0 375 U (35°) Dk. Matte 2 51-2 09 1 .2 1 7 376* II (60°) Brt Satin 1 62-1 68 1 .4 2 8 377* (55°) Satin 2 12-1 60 1 .3 2 0 378 (65°) Nr. Brt 1 92-1 13 1 .7 2 5 379* H n (70°) Semi -Brt 1 87-1 06 1 .8 2 9 380 m (80°) Satin 1. 76-1 02 1 .7 4 2

High Temperature (65°^ PR Test (100 g/1 CrOj)

381 180-4-1/2 40-1 30-30 Nr. Brt 1 93-1 15 1 .7 2 1 382 60-1-1/2 Brt Satin 2 29-1 36 1 .7 2 6 383 40-1 Lt. Matte 2 02-1 27 1 .6 2 5 384 20-1/2 Matte 1 81-1 15 1 .6 2 6 385 60-6 20-1 30-15 Satin 1 52-0 91 1 .7 2 5 386 40-4 II H Matte 1 75-0 98 1 .8 3 2 387* 20-2 H M Dk. Matte 1 14-0 70 1 .6 3 5 388 120-12 Brt Satin 1 20-0 83 1 .5 3 2 389 120-2 30-90 Semi -Brt 1 89-1 04 1 .8 2 8 390 60-1 Brt Satin 1 77-1 04 1 .7 2 6 391 40-2/3 II Matte 1. 61-0 87 1 .8 2 4

* Make-up additions of Cr03 Burnt edyos

** Based on current differences between forward and reverse parts of cycle

Note: K= Kocour thickness measurement

M» Micrometer me.i'.urenient at extreme edges and central area of specimen

Test PR Cycle Effective Current Cr Cr Thickness Ratio

No. For. -Rev. Cycle** Density Surface Edge-Ctr (K) (Ml (sec) For. -Rev. (mil)

(asd)

High Temperature (65°) PR Test Cent. (100 g/1 Cr03)

Ok. Matte 1.41-0.90 1.6 2.5 392 20-1/3 20-1 30-90

High Reverse

393* 120-1-1/2 40-1 50-100

394 120-3 70-1 C\J I n 395* 120-4 15-1 H 396 120-6 10-1 N 397 120-7-1/2 8-1 398* 120-6 10-1 II 399 120-12 5-1 n 400* 120-10 6-1 11

Low Reverse

401 120-12 20-1

• 50-25 402* 120-16 II 403 120-24 10-1 II 404* 60-6 20-1 II 405* 40-4 n 405 20-2 II II 407* 120-6 40-1 n 408 II It N 409* 60-3 U n 410* 20-2 20-1 n

• Equal Reverse

411 20-1/2 40-1 50-50

412* 40-1 u 413 60-1-1/2 n 414* 180r4-l/2 II N 415 120-3 H n 416* 120-6 20-1 d 417 60-3 H 418 40-2 » M

Dilute bath + 25 g/1 419* 120-6 20-1 50-50 420 no PR 50- 421* 30- 422 120-6 20-1 30-30

Setni-Brt 2.89-2.21 1 .3 2 .6 Brt Satin 2.44-2.17 1 .1 1 5 Satin 2.54-1 .92 1 .3 1 8

II 1.76-1.16 1 .5 2 6

II 1.01-0.74 1 .4 1 6

u 1.27-0.99 1 .4 1 8 Brt Satin 0.05-0.03 2 0 1 3 Semi -Brt 0.05-0.05 1 0 T 0

Satin 2.48-2 .25 1 .1 1 .1

II 2.34-1 .82 1 .3 1 .4

II 1.97-1 57 1 .3 2 0 Lt. Matte 2.30-1 59 1 .4 1 6

II 2.64-1 92 1 .4 1 2 Matte 1.18-0 86 1 .4 2 6 Brt Satin 2.67-2 30 1 .2 1 4 Semi -Brt 2.06-1 52 1 .4 1 2 Satin 3.05-2 57 1 .3 1 1 Lt. totte 2.42-1 95 1 .2 1. 3

Matte 2.34-1.95 1 .2 1 .5 Lt. Matte 2.31-1.81 1 .3 • 1 .2

II 2.52-2.17 1 .2 1 .2 Brt Satin 2.20-2.03 1 .1 1 . 3 Semi -Brt 1.15-0.82 1 .4 1 .3 Satin 1.99-1.35 1 .5 1 .4

II 2.24-2.05 1 .1 1 .1 Lt. Matte 2.66-2.01 1 .3 1 .2 NaOH

Blistered, no Cr at edges -- Brt Cr Ctr, edges bare Brt* 1.47-1.15 1.3 1.6 Satin* 1.90-1.69 1.1 1.4

Test PR Cycle Effective Current Cr Cr Thickness Ratio

No. For. -Rev. Cycle** Density Surface Edge-Ctr. (K) (M) (sec) For. -Rev. (mil)

(asd)

New bath - 100 g/1 CrO.

423 no PR 30- Brt 1.60-1 13 1 .4' 1 .5 424 11 50- Semi -Brt 2.54-2 06 1 .2 1 .3 425* H M M 2.04-1 46 1 .4 1 .4 426 H 30- N 1.56-0 98 1 .6 1 .9

Dilute bath + 10 g/1 NaOH

427 no PR 50- Semi -Brt 2.27-1 95 1 .2 1 .3 428* ti m Nr. Brt 1.96-1 65 1 .2 1 .3 429 H 30- Brt 1.48-1 08 1 .4 1 .3 430 120-6 20-1 50-50 Lt. Matte 2.35-2 05 1 .1 1 .1 431 60-3 n Matte 2.23-2 07 1 .1 1 .1 432* 120-3 40-1 n -batin 2.55-2 08 1 .2 1 .1 433 180-4-1/2 Brt Satin 2.10-1 74 1 .2 1 .2 434* 40-1 n H Matte 2.60-2 16 1 .2 1 .2 435* 60-1-1/2 11 U Lt. Matte 2.53-2 17 1 .2 1 .3 436 120-6 II 50-25 Brt Satin 2.12-1 62 1 .3 1 .3 437* 20-1 Matte 2.06-1 71 1 .2 1 .4 438 T20-6 40-1 30-15 Satin 1.62-1 21 1 .3 1 .8" 435r* 120-1 II 30-90 II 1.55-1 24 1 3 1 .2 4^0 60-1 20-1 M Blk. 1 .49-0 61 2 4 1 .7 441* H H 1.67-0 61 2 7 3 .3 442 120-3 40-1 30-30 Satin 1.96-1 55 1 3 1 .5 443* 40-2 20-1 50-50 Matte* 2.54-2 03 1 2 1 .0 444 1C0-9 II Satin 2.13-1 76 1 2 1 .2 445 180-12 15-1 Brt Satin 1.S5-1 48 1 3 1 .1

* Make-up additions of CrOj.

+ Burnt eilrf^<;

.

(sec) For. -Rev. (niil) (asd)

446

448

449

450

451

120-6

120-3

No PR

No PR 120-3

Dilute Batli (100 g/1 Cr03)

20-1 40-1 50-50

50-

40-1 SOSO- 50

10 g/1 NaCl

Satin

Nr. Brt

Dilute Bath + 5 g/1 NaCl

Coarse Matte

Satin

2.6S-1.91 2.64-2.22

1.47-1. IS

2.25-1.63

3.14-2.56

1.4

1.2

1.3

1.4

1.2

2.2

1.2 1.3

1.6

1.3

453

454 455

456

457 458

459 460

461

462 463

464

465

466

467 468

469

No PR 120-3 120-6

120-6

120-3

No PR

No PR 120-6 120-3

No PR 120-6

No PR 120-3

120-6

120-6

120-3

No PR

40-1

20-1

20-1 40-1

SO- SO-SO

15 g/1 NaCl

SO-SO

soSatin

Lt. Matte

Satin

Coarse Matte

Brt Satin

20 g/1 NaCl

SO- Brt

20-1 SO-SO Cr Flaky

40-1 Satin

30 g/1 NaCl

SO- Grainy"

20-1 SO- 50 Flaked*

50- Brt*

40-1 50-50 Ctr Brt*

20-1

H Satin

High CD, Dilute Bath + NaCl

20r1 100-100 Brt*

40-1 Satin

100- Brt

2.58-2.25

2.80-2.36 2.16-1.94

2.45-1.76

2.02-1 .84 2.47-2.22

2.84- 3.52

1.85- 1.59

2.95-2.74 0.64-2.24

2.09-1 -73'

2.06-2.82

2.74-2.17 3.05-2.60

1 .2 1.2

1.1

1 .4 1.1 1.1

0.8

1.2

4.29-4.01 1.1

1.1

0.3. 1.2

0.7

1.3 1.2

1.0

1.4 1.0

1.1 1.0

1.1

0.9

1.0

2.2

1.1 0.7

1.1 0.6

.1.1

1.1 1.7

l.£

Test

No.

PR Cycle

For. -Rev.

(sec)

Effective Cycle**

Current

Density

For. -Rev.

(asd)

Cr Cr Thickness Ratio Surface Edge-Ctr. (K) (M) (mil)

High CD, .Bath (std. 250 g/1 Cr03) 470 No PR 100- Brt 2.26-1 70 1.3 5.0

471 120-6 20-1 100-ioo Lt. Matte 1 .89-1 34 1.4 l.S 472 120-3 40-1 Satin 2.39-1 71 1 .4 2.0 473 150-150 Lt. Matte 2.53-1 80 1.4 2.7 474 120-6 20-1 Satin 2.48-2 .03 1.2 2.3 475 No PR 150- Brt 2.69-2 35 1.1 1.8 476 60-3 20-1 150-150 Lt. Matte 1.84-1 58 1.2 3.S 477 90-6 15-1 Satin 1.34-1 00 1.3 2.2

High CD, Standard Bath + 20 g/1 NaOH

478 120-6 20-1 150-150 Satin 2.59-2 34 1.1 1.1 479 120-3 40-1 75-75 2.26-1 88 1.2 l.£ 480 150-150 Lt. Matte 2.25-1 77 1.3 2.C

481 No PR ~ ISO- Satin 2.25-1 70 1.3 1.9

High Temperature + UaOH (10 g/1 ) (Dll. 100 g/1 Cr03) 482 120-3 40-1 50-50 Satin 1.97-1 .55 1.3 1.5 483 No PR 50- Nr. Brt 2.26-1 79 1.3 1.6 484 120-6 20-1 50-50 Satin 1.76-1 70 1.0 i.e 485 60-3 20-1 1.97-1 .49 1.3 1.2 486 120-3 80-1 50-25 Brt Satin 2.06-1 73 1.2 1.2 487 180-3 120-1 Semi -Brt 2.31-1 85 1.3 1.4 488 180-6 60-1 a 1.67-1 28 1.3 1.3

Dilute Dath + 10 g/1 NaCOj

489 No PR 50- Brt Satin 2.13-1 80 1.2 1.7 490 120-6 40-1 50-25 Satin 2.21-1 59 1.4 1.9

491 120-3 80-1 2.26-1 66 1.4 1.3

20 g/1 NaCOa

492 120-3 80-1 50-25 Brt Satin 2.18-1 87 1.2 1.6 493 120-6 40-1 Satin 1.88-1 45 1.3 1.1

Dilute Bath + 10 g/1 NaCOj + 10 g/1 Nj2 MO4

494 120-3 80-1 50-25 Ok. Matte 0.57-0 59 1.0 1.1 495 No FR bO- 1.4U-1 15 1.3 496 12C-6 40-1 50-25 Ma tie* 1.J4-0 tM 1.6 1 .[ 4r7 Itu-C 60-

U l.cl-1 U'J 1 .5 "» I

Cr PUTED TtLHEiDS

Test

Uo. PR CycleFor. -Rev.

( sec

)

Effective Curi-ont » Cr Thickness Ratio Cycle iJcnsity Top and bottom \l^"-2^

For. -Rev. (asd)

Dilute ilOO g/1 Cr03) Bath (50 and 55'C)

J 1 20-3 40-1 50-50 4

2 1 20-6 20-1 4

3 No PR 50 3.5

4 1 20-9 15-1 50-50 4

Dilute Bath (55°C)

16 1 20-3 20-1 30-60 i

17 No PR 30 3.5

18 120-16 15-1 50-25 4

Dilute Bath + 10 g/1 NaOH (50-55°C)

5 1 20-C 20-1 50-60 7 6 40-1 50-25 8

7 120-3 20-1 50-100 2.3 8

» 30-60 2 9

U 4

10 No PR 30' 2

11 120-6 40-1 30-15 2

12 20-10 • 1.5

13 120-9 25-1 30-15 2.5

14 li 60-25 4

Dilute Bath + NaOH (65°C)

15 120-12 20-1 50-25 2.5

19 120-16 15-1 6

20 .No PR 30 2.5

Std. Bath (250 g/1 CrOj) 65°C

21 No PR 30 2.7

CC 80-1 30-15 3

23 20-1 30-60 1.3

24 120-6 20-1 50-50 4 25 60-3 3

26 120-6 30-30 2

27 30-1-1/2 50-50 4

28 120-5 50-65 2 29 40-2 H 50-50 4

Std. Bath + Na0H-65°C

30 120-3 20-1 30-60 1.3

31 No PR 50 5 32 120-5 20-1 50-60 3.5

33 No PR 30 3 34 120-12 20-1 50-25 5 35 120-6 40-1 •1 6

Test Pulse

No. On-Off

(millisec)

Pulse

Control

(volts, amp)

Base Level

(Z of Pulse Voltage) Temp - Cr Cr Thickness Ratio Current Density Surface Edge to Ctr.

(asd) (mils)

533 90-10 V 5 65/30 Coarse matte 1.5

534 80-20 V 0

II Matte 2.5

535 V 20 H Satin 1.8

536 V 30 H Brt satin 2.3

537 V 35 II 3.0

538 50-50 V

H U Semi-brt 2.8

639 N V 50 3.0

540 V 25 H Matte 2.2

541 m V 65/45 Drt 2.0

542 V

U 65/60 Brt satin 1.3

643 10-10 V 50 65/45 Matte 1.5

544 « V

II Ncar-lirt 2.1 545 m V 25 n I'-JttC 1.5

546 m A

II i> Brt satin 2.0

547 None 100 n Ncar-brt 3.1 543 65/30 2.6

Test De;osits vn'th Thictness Ratios less than 2.5

Test Pulse

No. on-cff

(mi 11 isec.

)

Pulse

Contrcl (Volt-A-D.)

Base Level

'i pulse level

)

Temp-CD.

("C/asd)

Cr Surface

Variable Pulse Test (cont.] 549 50-10 V 25 65/45

551 40-10 V

M 653 30-10 V

H II 554 20-10 V

n n 555 15-10 V

n M 656 10-10 V

R 559 10-20 V

n It 560 10-30 V U 563 5-5 V

' n n 565 2-2 V

n It 569 1-J.5 V

n n 671 0.5-0.2 V

R a 572 lOO-O 100 « 573 w 55/45

575 3-2 "v 25

676 3-1 V

a U 580 20-10 V

M 582 50-50 V

a M 583 30-30 V

M f1 586 30-50 A

M 587 10-10 A

H 588 5-5 A

«

Base Voltage Level

B

Test

590 10-10 V 33 55/45

592 2-10 V

n 594 3-15 A

n

Brt Satin Satin

Matte

Satin Matte

Satin

Lt. Matte

Brt Satin Matte

Ser.i- Brt Brt

Lt. Matte Matte

Nr. Brt Matte

Lt. Matte Satin

Matte

Nr. Brite

Brt

Cr Thickness

Ratio Edgo-Ctr.

(mils)

2.4

2.1

2.3

2.1 2.0

2.1 2.0

2.4

2.4

2.3 1.8

Test Deposits vlth Thickness Ratios less than 2.5

Test Pulse Pulse Base Level Temp-CD. Cr Efficiency* Cr Thickness

Ko

.

on-off . Control (Z pulse level) (°C/asd) Surface (%) R^tio

(mlllisec.) (VoU-Ar.p.) Edge- Ctr. (mils)

Base Vcltage Level Test Jjv!25.

595 4-20 V 33 55/45 Brt 11. 9 1. 5 597 5-15 V

II . It Matte 7. 0 1. 9 598 7-21 V

II II Semi-Brt 9. 8 2. 3 599 7-21 V 40 " Nr-rsrt 8 1 1. 8 600 7-21 V 45 Brt 9. 5 2. 4 601 7-21 V 50 " 11 12. 3 2.4

651 7-21 V 60 " 13. 0 1, 7 603 7-21 V 75 " II 14. 4 1. 4 604 7-21 V 26 Matte 6 2. 3 6S2 7-21 V 33 Scmi-Brt 6 9 2. 0 650 7-21 V 75 Brt 14. 0 1. 9 659 7-21 V 40 9. 7 2. 0 657 7-21 V 5* Scmi-Brt 11 9 2. 2

Pulse Ratio Test

607 10-30 V 33 55/45 Matte 6 1 2. 0

608 12-36 V 9 8 2. 2 653 16-48 V Satin 11 8 2. 0 613 20-60 V Mntte 10 0 1. 6 61A 30-60 V Satin 8 7 2. 1 615 50-60 V 8 I, 2. 0 654 50-5.0 V Scml-Ert 10 1 1. 8 619 10-iO V Lt. Matte 10 5 1. 7 620 10-60 V Scnil -lift 6 5 2. 1 621 8-48 V Nr-llrt } 1 2 1 622 15-75 V Lt. Hjtte ') 2 2 654 50-50 V

• Si:ml-l'.rt ') 9 1 8 624 9-J6 V S.illn 7 2 2 2 625 3-15 V lirt 8 1 2 ^ €26 100-0 9 2

Test Deposits with Thickness Ratios less than 2.5 (cont'd.) Test Pulse Pulse Base Level Temp-CD. Cr Efficiency* Cr Thickness

No. on-off Control (Z pulse level) CC/asd) Surface (J) Ratio

(nillisec.) (Volt-Amp.) Edgc-Ctr.

(mils)

Pulse Ratio Test (cont 'd.

)

628 X J —i,UU V 629 25-100 V

ft 6S6 10-30 V 50

631 15-75 V

II 632 12-60 V • < 633 10-50 V

II 634 10-40 V

n 635 10-20 V

It 636 10—10 V

II 637 10-5 ft 633 10-33 V

It 639 15-15 V

It 641 25-5 V

I 6A2 50-5 V

1 643 100-5 V

644 20-60 V . fl 645 9-36 V

ft 646 50-60 V

It 647 30-60 V

t

648 12-48 V

if 650 12-36 V

II

Duplicates of

658 3-15 V 33 661 20-60 V

II 662 10-50 V

It 663 10-5 V

It 664 15-15 V

If

55/45

Semi-Brt Brt-Satin

Brt Brt-Satin

Nr-Brt

Brt

Nr-Brt

Brt

Nr-Brt

Brt

Semi-Brt

Brt Brt-Satin

Semi-Brt

Brt Nr-Brt

Brt Satin

Nr-Brt

Brt Nr-Ert

9.6

10.5 12.4

12.4

13.5 11.7

11.2 9.9

11.4 11.8

10.9

14.1

12.2

12.2 14.5

10.9 11.7

13.0

12.8 12.8

9.2

10.3

9.9 11.2

11.0 11.1

2.1

1.7

2.2 2.2 2.1

2.0

2.0

2.2

2.2

1.7 1.9

1.7

2.2 2.2

2.2

2.0

2.2

2.2 2.0

1.8 2.0

'2.0 2.x

1.8

1.7

1.9

Test

No.

Teat Deposits with Thickness Ratios less than 2.5 (cont'd.)

Pulse

on-off

(mlllisec.)

Pulse

Control

(Volt-Amp.)

Base Level

(2 pulse level) Temp-CD.

(°C/asd) Cr Surface Efficiency*

(Z) Cr Thickness

Ratio

Edge-Ctr.

(mils)

Duplicates of Low Ratio Deposits (cont'd.)

665 10-30 V 25 " Matte 8.6 2.0

666 25-100 V 50 " Nr-Brt 11.5 1.8

667 4-20 V 33 " Brt 9.7 2.3

668 15-15 V 50 " Nr-Brt 11.4 1.8

669 10-5 V " " " 11.0 2.0

* The deposition efficiency is determined from the thickness of the Cr near the center of the panel, and

Che value is thus somewhat affected by the distribution of the deposit.

Xest Pulse Pulse Base Level Temp-CD. Cr Efficiency Cr Thickness

No. on-off Control (J pulse level) ("C/asd) Surface Z Ratio

(mlllisec.) (Volt-Amp.) Edge-Ctr.

Duplication of Low Ratio Deposits (cont.)

670 4-20 V 33 55/45 Seral-brt. 9.3 2.2

671 4-20 V

II II Brt. 10.6 2.4

672 25-75 V SO

II Brt. 13.2 1.9

.673 100-0 n Brt. 11.7 2.5

674 16-48 V 33 It Satin 9.3 1.7

67S 16-48 A

II ft Seml-brt. 1:3.9 1.8

Dilute Bath - (100 g/1 Cr03)

676 16-48 V 33 55/45 Nr. brt. 12.7 1.4

677 25-100 V

1 II Brt. 11.8 X.3

678 15-15 V . SO 11 Lt. matte 13.7 1.8

679 100-0 n Brt. 14.9 1.6

680 10-5 V SO tt tl 12.2 1.3

681 3-15 V .33 II n 9.7 0.9

682 50-50 V

H n II 12.4 1.2

683 7-21 V 75

tt 13.4 1.2

68A 10-30 V 25 65/45 Nr. brt. 7.0 1.5

Concentrated Bath - (500 g/1 Cr03)

68S 3-15 7 33 55/45 matte 7.3 3.9

686 50-50 V

II II 11.4 2.8

687 7-21 T 7S It • Nr, brt. 7.0 5.6

688 10-5 V 50 matte 12.2 3.3

689 25-100 V 33 If tt 8.5 3.8

690 16-48 V

1 If tt 8.1 2.7

691 100-0 n Nr. brt. 6.8 7.4

692 10-30 V 2S It Satin 12.9 1.6

Test Pulse Pulse BaseLevel Temp-CD. Cr Efficiency Or Thickness

Ho. on-off Control (Z pulse level) (°C/asd) Surface Z Ratio

(mlllisec.) (Volt-Amp.) Edge-Ctr.

Current Controlled Pulse

693 3-15 A 33 55/45 Brt. 9.5 , 2.0

694 15-15 A 50 " Brt. 14.0 2.4

695 25-100 A 33 " " U.6 2.0



I